diff --git a/packages/connector-alipay-native/src/index.test.ts b/packages/connector-alipay-native/src/index.test.ts
index f95e7ec02..11f584307 100644
--- a/packages/connector-alipay-native/src/index.test.ts
+++ b/packages/connector-alipay-native/src/index.test.ts
@@ -1,12 +1,16 @@
-import { ConnectorError, ConnectorErrorCodes, GetConnectorConfig } from '@logto/connector-types';
+import {
+  ConnectorError,
+  ConnectorErrorCodes,
+  GetConnectorConfig,
+  ValidateConfig,
+} from '@logto/connector-types';
 import nock from 'nock';
 
 import AlipayNativeConnector from '.';
 import { alipayEndpoint } from './constant';
 import { mockedAlipayNativeConfig, mockedAlipayNativeConfigWithValidPrivateKey } from './mock';
-import { AlipayNativeConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<AlipayNativeConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const alipayNativeMethods = new AlipayNativeConnector(getConnectorConfig);
 
@@ -15,18 +19,30 @@ describe('validateConfig', () => {
     jest.clearAllMocks();
   });
 
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
   it('should pass on valid config', async () => {
-    await expect(
-      alipayNativeMethods.validateConfig(mockedAlipayNativeConfig)
-    ).resolves.not.toThrow();
+    const validator: ValidateConfig = alipayNativeMethods.validateConfig;
+    expect(() => {
+      validator(mockedAlipayNativeConfig);
+    }).not.toThrow();
   });
 
-  it('should throw on empty config', async () => {
-    await expect(alipayNativeMethods.validateConfig({})).rejects.toThrowError();
+  it('should fail on empty config', async () => {
+    const validator: ValidateConfig = alipayNativeMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
 
-  it('should throw when missing required properties', async () => {
-    await expect(alipayNativeMethods.validateConfig({ appId: 'appId' })).rejects.toThrowError();
+  it('should fail when missing required properties', async () => {
+    const validator: ValidateConfig = alipayNativeMethods.validateConfig;
+    expect(() => {
+      validator({ appId: 'appId' });
+    }).toThrow();
   });
 });
 
diff --git a/packages/connector-alipay-native/src/index.ts b/packages/connector-alipay-native/src/index.ts
index 8dd8602bc..baaadbd33 100644
--- a/packages/connector-alipay-native/src/index.ts
+++ b/packages/connector-alipay-native/src/index.ts
@@ -13,7 +13,6 @@ import {
   ConnectorMetadata,
   GetAuthorizationUri,
   GetUserInfo,
-  ValidateConfig,
   SocialConnector,
   GetConnectorConfig,
 } from '@logto/connector-types';
@@ -44,23 +43,27 @@ import { signingParameters } from './utils';
 
 export type { AlipayNativeConfig } from './types';
 
-export default class AlipayNativeConnector implements SocialConnector {
+export default class AlipayNativeConnector implements SocialConnector<AlipayNativeConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
 
   private readonly signingParameters = signingParameters;
 
-  constructor(public readonly getConfig: GetConnectorConfig<AlipayNativeConfig>) {}
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is AlipayNativeConfig {
     const result = alipayNativeConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public getAuthorizationUri: GetAuthorizationUri = async ({ state }) => {
-    const { appId } = await this.getConfig(this.metadata.id);
+    const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
+    const { appId } = config;
 
     const queryParameters = new URLSearchParams({ app_id: appId, state });
 
@@ -108,6 +111,9 @@ export default class AlipayNativeConnector implements SocialConnector {
   public getUserInfo: GetUserInfo = async (data) => {
     const { auth_code } = await this.authorizationCallbackHandler(data);
     const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
     const { accessToken } = await this.getAccessToken(auth_code, config);
 
     assert(
diff --git a/packages/connector-alipay/src/index.test.ts b/packages/connector-alipay/src/index.test.ts
index 41e1d8886..d6fff86bc 100644
--- a/packages/connector-alipay/src/index.test.ts
+++ b/packages/connector-alipay/src/index.test.ts
@@ -1,12 +1,16 @@
-import { ConnectorError, ConnectorErrorCodes, GetConnectorConfig } from '@logto/connector-types';
+import {
+  ConnectorError,
+  ConnectorErrorCodes,
+  GetConnectorConfig,
+  ValidateConfig,
+} from '@logto/connector-types';
 import nock from 'nock';
 
 import AlipayConnector from '.';
 import { alipayEndpoint, authorizationEndpoint } from './constant';
 import { mockedAlipayConfig, mockedAlipayConfigWithValidPrivateKey } from './mock';
-import { AlipayConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<AlipayConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const alipayMethods = new AlipayConnector(getConnectorConfig);
 
@@ -15,22 +19,34 @@ describe('validateConfig', () => {
     jest.clearAllMocks();
   });
 
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
   it('should pass on valid config', async () => {
-    await expect(
-      alipayMethods.validateConfig({
+    const validator: ValidateConfig = alipayMethods.validateConfig;
+    expect(() => {
+      validator({
         appId: 'appId',
         privateKey: 'privateKey',
         signType: 'RSA',
-      })
-    ).resolves.not.toThrow();
+      });
+    }).not.toThrow();
   });
 
-  it('should throw on empty config', async () => {
-    await expect(alipayMethods.validateConfig({})).rejects.toThrowError();
+  it('should fail on empty config', async () => {
+    const validator: ValidateConfig = alipayMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
 
-  it('should throw when missing required properties', async () => {
-    await expect(alipayMethods.validateConfig({ appId: 'appId' })).rejects.toThrowError();
+  it('should fail when missing required properties', async () => {
+    const validator: ValidateConfig = alipayMethods.validateConfig;
+    expect(() => {
+      validator({ appId: 'appId' });
+    }).toThrow();
   });
 });
 
diff --git a/packages/connector-alipay/src/index.ts b/packages/connector-alipay/src/index.ts
index 461dc784c..a6c09e27e 100644
--- a/packages/connector-alipay/src/index.ts
+++ b/packages/connector-alipay/src/index.ts
@@ -11,7 +11,6 @@ import {
   ConnectorMetadata,
   GetAuthorizationUri,
   GetUserInfo,
-  ValidateConfig,
   SocialConnector,
   GetConnectorConfig,
 } from '@logto/connector-types';
@@ -44,23 +43,27 @@ import { signingParameters } from './utils';
 
 export type { AlipayConfig } from './types';
 
-export default class AlipayConnector implements SocialConnector {
+export default class AlipayConnector implements SocialConnector<AlipayConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
 
   private readonly signingParameters = signingParameters;
 
-  constructor(public readonly getConfig: GetConnectorConfig<AlipayConfig>) {}
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is AlipayConfig {
     const result = alipayConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public getAuthorizationUri: GetAuthorizationUri = async ({ state, redirectUri }) => {
-    const { appId: app_id } = await this.getConfig(this.metadata.id);
+    const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
+    const { appId: app_id } = config;
 
     const redirect_uri = encodeURI(redirectUri);
 
@@ -116,6 +119,9 @@ export default class AlipayConnector implements SocialConnector {
   public getUserInfo: GetUserInfo = async (data) => {
     const { auth_code } = await this.authorizationCallbackHandler(data);
     const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
     const { accessToken } = await this.getAccessToken(auth_code, config);
 
     assert(
diff --git a/packages/connector-aliyun-dm/src/index.test.ts b/packages/connector-aliyun-dm/src/index.test.ts
index c54d3f5c2..76a667066 100644
--- a/packages/connector-aliyun-dm/src/index.test.ts
+++ b/packages/connector-aliyun-dm/src/index.test.ts
@@ -1,11 +1,10 @@
-import { GetConnectorConfig } from '@logto/connector-types';
+import { GetConnectorConfig, ValidateConfig } from '@logto/connector-types';
 
 import AliyunDmConnector from '.';
 import { mockedConfig } from './mock';
 import { singleSendMail } from './single-send-mail';
-import { AliyunDmConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<AliyunDmConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const aliyunDmMethods = new AliyunDmConnector(getConnectorConfig);
 
@@ -29,19 +28,28 @@ describe('validateConfig()', () => {
     jest.clearAllMocks();
   });
 
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
   it('should pass on valid config', async () => {
-    await expect(
-      aliyunDmMethods.validateConfig({
+    const validator: ValidateConfig = aliyunDmMethods.validateConfig;
+    expect(() => {
+      validator({
         accessKeyId: 'accessKeyId',
         accessKeySecret: 'accessKeySecret',
         accountName: 'accountName',
         templates: [],
-      })
-    ).resolves.not.toThrow();
+      });
+    }).not.toThrow();
   });
 
-  it('throws if config is invalid', async () => {
-    await expect(aliyunDmMethods.validateConfig({})).rejects.toThrow();
+  it('should fail if config is invalid', async () => {
+    const validator: ValidateConfig = aliyunDmMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
 });
 
diff --git a/packages/connector-aliyun-dm/src/index.ts b/packages/connector-aliyun-dm/src/index.ts
index 826a2fc0a..a5413a717 100644
--- a/packages/connector-aliyun-dm/src/index.ts
+++ b/packages/connector-aliyun-dm/src/index.ts
@@ -3,7 +3,6 @@ import {
   ConnectorErrorCodes,
   ConnectorMetadata,
   EmailSendMessageFunction,
-  ValidateConfig,
   EmailConnector,
   GetConnectorConfig,
 } from '@logto/connector-types';
@@ -19,24 +18,24 @@ import {
   sendMailErrorResponseGuard,
 } from './types';
 
-export default class AliyunDmConnector implements EmailConnector {
+export default class AliyunDmConnector implements EmailConnector<AliyunDmConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  constructor(public readonly getConfig: GetConnectorConfig<AliyunDmConfig>) {}
-
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is AliyunDmConfig {
     const result = aliyunDmConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   // eslint-disable-next-line complexity
   public sendMessage: EmailSendMessageFunction = async (address, type, data, config) => {
-    const emailConfig =
-      (config as AliyunDmConfig | undefined) ?? (await this.getConfig(this.metadata.id));
-    await this.validateConfig(emailConfig);
+    const emailConfig = config ?? (await this.getConfig(this.metadata.id));
+
+    this.validateConfig(emailConfig);
+
     const { accessKeyId, accessKeySecret, accountName, fromAlias, templates } = emailConfig;
     const template = templates.find((template) => template.usageType === type);
 
diff --git a/packages/connector-aliyun-sms/src/index.test.ts b/packages/connector-aliyun-sms/src/index.test.ts
index 65db6ad21..31840ac73 100644
--- a/packages/connector-aliyun-sms/src/index.test.ts
+++ b/packages/connector-aliyun-sms/src/index.test.ts
@@ -1,11 +1,10 @@
-import { GetConnectorConfig } from '@logto/connector-types';
+import { GetConnectorConfig, ValidateConfig } from '@logto/connector-types';
 
 import AliyunSmsConnector from '.';
 import { mockedConnectorConfig, mockedValidConnectorConfig, phoneTest, codeTest } from './mock';
 import { sendSms } from './single-send-text';
-import { AliyunSmsConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<AliyunSmsConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const aliyunSmsMethods = new AliyunSmsConnector(getConnectorConfig);
 
@@ -25,14 +24,23 @@ describe('validateConfig()', () => {
     jest.clearAllMocks();
   });
 
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
   it('should pass on valid config', async () => {
-    await expect(
-      aliyunSmsMethods.validateConfig(mockedValidConnectorConfig)
-    ).resolves.not.toThrow();
+    const validator: ValidateConfig = aliyunSmsMethods.validateConfig;
+    expect(() => {
+      validator(mockedValidConnectorConfig);
+    }).not.toThrow();
   });
 
-  it('throws if config is invalid', async () => {
-    await expect(aliyunSmsMethods.validateConfig({})).rejects.toThrow();
+  it('should fail if config is invalid', async () => {
+    const validator: ValidateConfig = aliyunSmsMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
 });
 
diff --git a/packages/connector-aliyun-sms/src/index.ts b/packages/connector-aliyun-sms/src/index.ts
index e341ae0ee..020f16aed 100644
--- a/packages/connector-aliyun-sms/src/index.ts
+++ b/packages/connector-aliyun-sms/src/index.ts
@@ -3,7 +3,6 @@ import {
   ConnectorErrorCodes,
   ConnectorMetadata,
   SmsSendMessageFunction,
-  ValidateConfig,
   SmsConnector,
   GetConnectorConfig,
 } from '@logto/connector-types';
@@ -14,23 +13,23 @@ import { defaultMetadata } from './constant';
 import { sendSms } from './single-send-text';
 import { aliyunSmsConfigGuard, AliyunSmsConfig, sendSmsResponseGuard } from './types';
 
-export default class AliyunSmsConnector implements SmsConnector {
+export default class AliyunSmsConnector implements SmsConnector<AliyunSmsConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  constructor(public readonly getConfig: GetConnectorConfig<AliyunSmsConfig>) {}
-
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is AliyunSmsConfig {
     const result = aliyunSmsConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public sendMessage: SmsSendMessageFunction = async (phone, type, { code }, config) => {
-    const smsConfig =
-      (config as AliyunSmsConfig | undefined) ?? (await this.getConfig(this.metadata.id));
-    await this.validateConfig(smsConfig);
+    const smsConfig = config ?? (await this.getConfig(this.metadata.id));
+
+    this.validateConfig(smsConfig);
+
     const { accessKeyId, accessKeySecret, signName, templates } = smsConfig;
     const template = templates.find(({ usageType }) => usageType === type);
 
diff --git a/packages/connector-apple/src/index.test.ts b/packages/connector-apple/src/index.test.ts
index a27862ad3..190bf903e 100644
--- a/packages/connector-apple/src/index.test.ts
+++ b/packages/connector-apple/src/index.test.ts
@@ -1,12 +1,16 @@
-import { ConnectorError, ConnectorErrorCodes, GetConnectorConfig } from '@logto/connector-types';
+import {
+  ConnectorError,
+  ConnectorErrorCodes,
+  GetConnectorConfig,
+  ValidateConfig,
+} from '@logto/connector-types';
 import { jwtVerify } from 'jose';
 
 import AppleConnector from '.';
 import { authorizationEndpoint } from './constant';
 import { mockedConfig } from './mock';
-import { AppleConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<AppleConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const appleMethods = new AppleConnector(getConnectorConfig);
 
@@ -40,12 +44,23 @@ describe('validateConfig', () => {
     jest.clearAllMocks();
   });
 
-  it('should pass on valid config', async () => {
-    await expect(appleMethods.validateConfig({ clientId: 'clientId' })).resolves.not.toThrow();
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
+  it('should be true on valid config', async () => {
+    const validator: ValidateConfig = appleMethods.validateConfig;
+    expect(() => {
+      validator({ clientId: 'clientId' });
+    }).not.toThrow();
   });
 
-  it('should throw on empty config', async () => {
-    await expect(appleMethods.validateConfig({})).rejects.toThrowError();
+  it('should be false on empty config', async () => {
+    const validator: ValidateConfig = appleMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
 });
 
diff --git a/packages/connector-apple/src/index.ts b/packages/connector-apple/src/index.ts
index d0c7396f1..7a33c565c 100644
--- a/packages/connector-apple/src/index.ts
+++ b/packages/connector-apple/src/index.ts
@@ -1,7 +1,6 @@
 import {
   ConnectorMetadata,
   GetAuthorizationUri,
-  ValidateConfig,
   GetUserInfo,
   ConnectorError,
   ConnectorErrorCodes,
@@ -14,22 +13,24 @@ import { scope, defaultMetadata, jwksUri, issuer, authorizationEndpoint } from '
 import { appleConfigGuard, AppleConfig, dataGuard } from './types';
 
 // TO-DO: support nonce validation
-export default class AppleConnector implements SocialConnector {
+export default class AppleConnector implements SocialConnector<AppleConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
 
-  constructor(public readonly getConfig: GetConnectorConfig<AppleConfig>) {}
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is AppleConfig {
     const result = appleConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public getAuthorizationUri: GetAuthorizationUri = async ({ state, redirectUri }) => {
     const config = await this.getConfig(this.metadata.id);
 
+    this.validateConfig(config);
+
     const queryParameters = new URLSearchParams({
       client_id: config.clientId,
       redirect_uri: redirectUri,
@@ -50,7 +51,11 @@ export default class AppleConnector implements SocialConnector {
       throw new ConnectorError(ConnectorErrorCodes.SocialIdTokenInvalid);
     }
 
-    const { clientId } = await this.getConfig(this.metadata.id);
+    const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
+    const { clientId } = config;
 
     try {
       const { payload } = await jwtVerify(idToken, createRemoteJWKSet(new URL(jwksUri)), {
diff --git a/packages/connector-facebook/src/index.test.ts b/packages/connector-facebook/src/index.test.ts
index 08f93b2cd..b2cd7f503 100644
--- a/packages/connector-facebook/src/index.test.ts
+++ b/packages/connector-facebook/src/index.test.ts
@@ -1,12 +1,16 @@
-import { ConnectorError, ConnectorErrorCodes, GetConnectorConfig } from '@logto/connector-types';
+import {
+  ConnectorError,
+  ConnectorErrorCodes,
+  GetConnectorConfig,
+  ValidateConfig,
+} from '@logto/connector-types';
 import nock from 'nock';
 
 import FacebookConnector from '.';
 import { accessTokenEndpoint, authorizationEndpoint, userInfoEndpoint } from './constant';
 import { clientId, clientSecret, code, dummyRedirectUri, fields, mockedConfig } from './mock';
-import { FacebookConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<FacebookConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const facebookMethods = new FacebookConnector(getConnectorConfig);
 
@@ -20,16 +24,29 @@ describe('facebook connector', () => {
       jest.clearAllMocks();
     });
 
+    /**
+     * Assertion functions always need explicit annotations.
+     * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+     */
+
     it('should pass on valid config', async () => {
-      await expect(
-        facebookMethods.validateConfig({ clientId, clientSecret })
-      ).resolves.not.toThrow();
+      const validator: ValidateConfig = facebookMethods.validateConfig;
+      expect(() => {
+        validator({ clientId, clientSecret });
+      }).not.toThrow();
     });
 
-    it('should throw on invalid config', async () => {
-      await expect(facebookMethods.validateConfig({})).rejects.toThrow();
-      await expect(facebookMethods.validateConfig({ clientId })).rejects.toThrow();
-      await expect(facebookMethods.validateConfig({ clientSecret })).rejects.toThrow();
+    it('should fail on invalid config', async () => {
+      const validator: ValidateConfig = facebookMethods.validateConfig;
+      expect(() => {
+        validator({});
+      }).toThrow();
+      expect(() => {
+        validator({ clientId });
+      }).toThrow();
+      expect(() => {
+        validator({ clientSecret });
+      }).toThrow();
     });
   });
 
diff --git a/packages/connector-facebook/src/index.ts b/packages/connector-facebook/src/index.ts
index dd4fbcf55..fcd16b8e4 100644
--- a/packages/connector-facebook/src/index.ts
+++ b/packages/connector-facebook/src/index.ts
@@ -9,7 +9,6 @@ import {
   ConnectorMetadata,
   GetAuthorizationUri,
   GetUserInfo,
-  ValidateConfig,
   SocialConnector,
   GetConnectorConfig,
   codeWithRedirectDataGuard,
@@ -33,22 +32,24 @@ import {
   userInfoResponseGuard,
 } from './types';
 
-export default class FacebookConnector implements SocialConnector {
+export default class FacebookConnector implements SocialConnector<FacebookConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
 
-  constructor(public readonly getConfig: GetConnectorConfig<FacebookConfig>) {}
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is FacebookConfig {
     const result = facebookConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public getAuthorizationUri: GetAuthorizationUri = async ({ state, redirectUri }) => {
     const config = await this.getConfig(this.metadata.id);
 
+    this.validateConfig(config);
+
     const queryParameters = new URLSearchParams({
       client_id: config.clientId,
       redirect_uri: redirectUri,
@@ -61,9 +62,11 @@ export default class FacebookConnector implements SocialConnector {
   };
 
   public getAccessToken = async (code: string, redirectUri: string) => {
-    const { clientId: client_id, clientSecret: client_secret } = await this.getConfig(
-      this.metadata.id
-    );
+    const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
+    const { clientId: client_id, clientSecret: client_secret } = config;
 
     const httpResponse = await got.get(accessTokenEndpoint, {
       searchParams: {
diff --git a/packages/connector-github/src/index.test.ts b/packages/connector-github/src/index.test.ts
index e0fa41803..31939be71 100644
--- a/packages/connector-github/src/index.test.ts
+++ b/packages/connector-github/src/index.test.ts
@@ -1,13 +1,17 @@
-import { ConnectorError, ConnectorErrorCodes, GetConnectorConfig } from '@logto/connector-types';
+import {
+  ConnectorError,
+  ConnectorErrorCodes,
+  GetConnectorConfig,
+  ValidateConfig,
+} from '@logto/connector-types';
 import nock from 'nock';
 import * as qs from 'query-string';
 
 import GithubConnector from '.';
 import { accessTokenEndpoint, authorizationEndpoint, userInfoEndpoint } from './constant';
 import { mockedConfig } from './mock';
-import { GithubConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<GithubConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const githubMethods = new GithubConnector(getConnectorConfig);
 
@@ -67,18 +71,30 @@ describe('validateConfig', () => {
     jest.clearAllMocks();
   });
 
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
   it('should pass on valid config', async () => {
-    await expect(
-      githubMethods.validateConfig({ clientId: 'clientId', clientSecret: 'clientSecret' })
-    ).resolves.not.toThrow();
+    const validator: ValidateConfig = githubMethods.validateConfig;
+    expect(() => {
+      validator({ clientId: 'clientId', clientSecret: 'clientSecret' });
+    }).not.toThrow();
   });
 
-  it('should throw on empty config', async () => {
-    await expect(githubMethods.validateConfig({})).rejects.toThrowError();
+  it('should fail on empty config', async () => {
+    const validator: ValidateConfig = githubMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
 
-  it('should throw when missing clientSecret', async () => {
-    await expect(githubMethods.validateConfig({ clientId: 'clientId' })).rejects.toThrowError();
+  it('should fail when missing clientSecret', async () => {
+    const validator: ValidateConfig = githubMethods.validateConfig;
+    expect(() => {
+      validator({ clientId: 'clientId' });
+    }).toThrow();
   });
 });
 
diff --git a/packages/connector-github/src/index.ts b/packages/connector-github/src/index.ts
index caf97fb28..6cb14a36b 100644
--- a/packages/connector-github/src/index.ts
+++ b/packages/connector-github/src/index.ts
@@ -1,7 +1,6 @@
 import {
   ConnectorMetadata,
   GetAuthorizationUri,
-  ValidateConfig,
   GetUserInfo,
   ConnectorError,
   ConnectorErrorCodes,
@@ -29,22 +28,24 @@ import {
   userInfoResponseGuard,
 } from './types';
 
-export default class GithubConnector implements SocialConnector {
+export default class GithubConnector implements SocialConnector<GithubConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
 
-  constructor(public readonly getConfig: GetConnectorConfig<GithubConfig>) {}
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is GithubConfig {
     const result = githubConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public getAuthorizationUri: GetAuthorizationUri = async ({ state, redirectUri }) => {
     const config = await this.getConfig(this.metadata.id);
 
+    this.validateConfig(config);
+
     const queryParameters = new URLSearchParams({
       client_id: config.clientId,
       redirect_uri: redirectUri,
@@ -56,9 +57,11 @@ export default class GithubConnector implements SocialConnector {
   };
 
   public getAccessToken = async (code: string) => {
-    const { clientId: client_id, clientSecret: client_secret } = await this.getConfig(
-      this.metadata.id
-    );
+    const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
+    const { clientId: client_id, clientSecret: client_secret } = config;
 
     const httpResponse = await got.post({
       url: accessTokenEndpoint,
diff --git a/packages/connector-google/src/index.test.ts b/packages/connector-google/src/index.test.ts
index be53d3d2f..4766725d6 100644
--- a/packages/connector-google/src/index.test.ts
+++ b/packages/connector-google/src/index.test.ts
@@ -1,12 +1,16 @@
-import { ConnectorError, ConnectorErrorCodes, GetConnectorConfig } from '@logto/connector-types';
+import {
+  ConnectorError,
+  ConnectorErrorCodes,
+  GetConnectorConfig,
+  ValidateConfig,
+} from '@logto/connector-types';
 import nock from 'nock';
 
 import GoogleConnector from '.';
 import { accessTokenEndpoint, authorizationEndpoint, userInfoEndpoint } from './constant';
 import { mockedConfig } from './mock';
-import { GoogleConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<GoogleConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const googleMethods = new GoogleConnector(getConnectorConfig);
 
@@ -20,18 +24,29 @@ describe('google connector', () => {
       jest.clearAllMocks();
     });
 
+    /**
+     * Assertion functions always need explicit annotations.
+     * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+     */
+
     it('should pass on valid config', async () => {
-      await expect(
-        googleMethods.validateConfig({ clientId: 'clientId', clientSecret: 'clientSecret' })
-      ).resolves.not.toThrow();
+      const validator: ValidateConfig = googleMethods.validateConfig;
+      expect(() => {
+        validator({ clientId: 'clientId', clientSecret: 'clientSecret' });
+      }).not.toThrow();
     });
 
-    it('should throw on invalid config', async () => {
-      await expect(googleMethods.validateConfig({})).rejects.toThrow();
-      await expect(googleMethods.validateConfig({ clientId: 'clientId' })).rejects.toThrow();
-      await expect(
-        googleMethods.validateConfig({ clientSecret: 'clientSecret' })
-      ).rejects.toThrow();
+    it('should fail on invalid config', async () => {
+      const validator: ValidateConfig = googleMethods.validateConfig;
+      expect(() => {
+        validator({});
+      }).toThrow();
+      expect(() => {
+        validator({ clientId: 'clientId' });
+      }).toThrow();
+      expect(() => {
+        validator({ clientSecret: 'clientSecret' });
+      }).toThrow();
     });
   });
 
diff --git a/packages/connector-google/src/index.ts b/packages/connector-google/src/index.ts
index 05f27ea82..817569fe6 100644
--- a/packages/connector-google/src/index.ts
+++ b/packages/connector-google/src/index.ts
@@ -8,7 +8,6 @@ import {
   GetAuthorizationUri,
   GetUserInfo,
   ConnectorMetadata,
-  ValidateConfig,
   SocialConnector,
   GetConnectorConfig,
   codeWithRedirectDataGuard,
@@ -31,22 +30,24 @@ import {
   userInfoResponseGuard,
 } from './types';
 
-export default class GoogleConnector implements SocialConnector {
+export default class GoogleConnector implements SocialConnector<GoogleConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
 
-  constructor(public readonly getConfig: GetConnectorConfig<GoogleConfig>) {}
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is GoogleConfig {
     const result = googleConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public getAuthorizationUri: GetAuthorizationUri = async ({ state, redirectUri }) => {
     const config = await this.getConfig(this.metadata.id);
 
+    this.validateConfig(config);
+
     const queryParameters = new URLSearchParams({
       client_id: config.clientId,
       redirect_uri: redirectUri,
@@ -59,7 +60,11 @@ export default class GoogleConnector implements SocialConnector {
   };
 
   public getAccessToken = async (code: string, redirectUri: string) => {
-    const { clientId, clientSecret } = await this.getConfig(this.metadata.id);
+    const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
+    const { clientId, clientSecret } = config;
 
     // Note：Need to decodeURIComponent on code
     // https://stackoverflow.com/questions/51058256/google-api-node-js-invalid-grant-malformed-auth-code
diff --git a/packages/connector-sendgrid-mail/src/index.test.ts b/packages/connector-sendgrid-mail/src/index.test.ts
index 354458130..2154b2c4e 100644
--- a/packages/connector-sendgrid-mail/src/index.test.ts
+++ b/packages/connector-sendgrid-mail/src/index.test.ts
@@ -1,10 +1,10 @@
-import { GetConnectorConfig } from '@logto/connector-types';
+import { GetConnectorConfig, ValidateConfig } from '@logto/connector-types';
 
 import SendGridMailConnector from '.';
 import { mockedConfig } from './mock';
-import { ContextType, SendGridMailConfig } from './types';
+import { ContextType } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<SendGridMailConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const sendGridMailMethods = new SendGridMailConnector(getConnectorConfig);
 
@@ -19,9 +19,15 @@ describe('validateConfig()', () => {
     jest.clearAllMocks();
   });
 
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
   it('should pass on valid config', async () => {
-    await expect(
-      sendGridMailMethods.validateConfig({
+    const validator: ValidateConfig = sendGridMailMethods.validateConfig;
+    expect(() => {
+      validator({
         apiKey: 'apiKey',
         fromEmail: 'noreply@logto.test.io',
         fromName: 'Logto Test',
@@ -33,11 +39,14 @@ describe('validateConfig()', () => {
             content: 'This is for testing purposes only. Your passcode is {{code}}.',
           },
         ],
-      })
-    ).resolves.not.toThrow();
+      });
+    }).not.toThrow();
   });
 
-  it('throws if config is invalid', async () => {
-    await expect(sendGridMailMethods.validateConfig({})).rejects.toThrow();
+  it('should be false if config is invalid', async () => {
+    const validator: ValidateConfig = sendGridMailMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
 });
diff --git a/packages/connector-sendgrid-mail/src/index.ts b/packages/connector-sendgrid-mail/src/index.ts
index 1dcc12f33..c2b5a55ee 100644
--- a/packages/connector-sendgrid-mail/src/index.ts
+++ b/packages/connector-sendgrid-mail/src/index.ts
@@ -3,7 +3,6 @@ import {
   ConnectorErrorCodes,
   ConnectorMetadata,
   EmailSendMessageFunction,
-  ValidateConfig,
   EmailConnector,
   GetConnectorConfig,
 } from '@logto/connector-types';
@@ -20,22 +19,23 @@ import {
   PublicParameters,
 } from './types';
 
-export default class SendGridMailConnector implements EmailConnector {
+export default class SendGridMailConnector implements EmailConnector<SendGridMailConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  constructor(public readonly getConfig: GetConnectorConfig<SendGridMailConfig>) {}
-
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is SendGridMailConfig {
     const result = sendGridMailConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public sendMessage: EmailSendMessageFunction = async (address, type, data) => {
     const config = await this.getConfig(this.metadata.id);
-    await this.validateConfig(config);
+
+    this.validateConfig(config);
+
     const { apiKey, fromEmail, fromName, templates } = config;
     const template = templates.find((template) => template.usageType === type);
 
diff --git a/packages/connector-smtp/src/index.test.ts b/packages/connector-smtp/src/index.test.ts
index 03de6dd80..24d504d1c 100644
--- a/packages/connector-smtp/src/index.test.ts
+++ b/packages/connector-smtp/src/index.test.ts
@@ -1,9 +1,8 @@
-import { GetConnectorConfig } from '@logto/connector-types';
+import { GetConnectorConfig, ValidateConfig } from '@logto/connector-types';
 
 import SmtpConnector from '.';
-import { SmtpConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<SmtpConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const smtpMethods = new SmtpConnector(getConnectorConfig);
 
@@ -12,9 +11,15 @@ describe('validateConfig()', () => {
     jest.clearAllMocks();
   });
 
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
   it('should pass on valid config', async () => {
-    await expect(
-      smtpMethods.validateConfig({
+    const validator: ValidateConfig = smtpMethods.validateConfig;
+    expect(() => {
+      validator({
         host: 'smtp.testing.com',
         port: 80,
         password: 'password',
@@ -46,11 +51,14 @@ describe('validateConfig()', () => {
             usageType: 'ForgotPassword',
           },
         ],
-      })
-    ).resolves.not.toThrow();
+      });
+    }).not.toThrow();
   });
 
-  it('throws if config is invalid', async () => {
-    await expect(smtpMethods.validateConfig({})).rejects.toThrow();
+  it('should be false if config is invalid', async () => {
+    const validator: ValidateConfig = smtpMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
 });
diff --git a/packages/connector-smtp/src/index.ts b/packages/connector-smtp/src/index.ts
index c477275eb..6d7c9875a 100644
--- a/packages/connector-smtp/src/index.ts
+++ b/packages/connector-smtp/src/index.ts
@@ -3,7 +3,6 @@ import {
   ConnectorErrorCodes,
   ConnectorMetadata,
   EmailSendMessageFunction,
-  ValidateConfig,
   EmailConnector,
   GetConnectorConfig,
 } from '@logto/connector-types';
@@ -14,22 +13,24 @@ import SMTPTransport from 'nodemailer/lib/smtp-transport';
 import { defaultMetadata } from './constant';
 import { ContextType, smtpConfigGuard, SmtpConfig } from './types';
 
-export default class SmtpConnector implements EmailConnector {
+export default class SmtpConnector implements EmailConnector<SmtpConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
 
-  constructor(public readonly getConfig: GetConnectorConfig<SmtpConfig>) {}
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is SmtpConfig {
     const result = smtpConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public sendMessage: EmailSendMessageFunction = async (address, type, data) => {
     const config = await this.getConfig(this.metadata.id);
-    await this.validateConfig(config);
+
+    this.validateConfig(config);
+
     const { host, port, username, password, fromEmail, replyTo, templates } = config;
     const template = templates.find((template) => template.usageType === type);
 
diff --git a/packages/connector-twilio-sms/src/index.test.ts b/packages/connector-twilio-sms/src/index.test.ts
index d6afc7c30..703cafd01 100644
--- a/packages/connector-twilio-sms/src/index.test.ts
+++ b/packages/connector-twilio-sms/src/index.test.ts
@@ -1,10 +1,9 @@
-import { GetConnectorConfig } from '@logto/connector-types';
+import { GetConnectorConfig, ValidateConfig } from '@logto/connector-types';
 
 import TwilioSmsConnector from '.';
 import { mockedConfig } from './mock';
-import { TwilioSmsConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<TwilioSmsConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const twilioSmsMethods = new TwilioSmsConnector(getConnectorConfig);
 
@@ -13,11 +12,22 @@ describe('validateConfig()', () => {
     jest.clearAllMocks();
   });
 
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
   it('should pass on valid config', async () => {
-    await expect(twilioSmsMethods.validateConfig(mockedConfig)).resolves.not.toThrow();
+    const validator: ValidateConfig = twilioSmsMethods.validateConfig;
+    expect(() => {
+      validator(mockedConfig);
+    }).not.toThrow();
   });
 
   it('throws if config is invalid', async () => {
-    await expect(twilioSmsMethods.validateConfig({})).rejects.toThrow();
+    const validator: ValidateConfig = twilioSmsMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
 });
diff --git a/packages/connector-twilio-sms/src/index.ts b/packages/connector-twilio-sms/src/index.ts
index 42c831c70..a1006cc29 100644
--- a/packages/connector-twilio-sms/src/index.ts
+++ b/packages/connector-twilio-sms/src/index.ts
@@ -3,7 +3,6 @@ import {
   ConnectorErrorCodes,
   ConnectorMetadata,
   EmailSendMessageFunction,
-  ValidateConfig,
   SmsConnector,
   GetConnectorConfig,
 } from '@logto/connector-types';
@@ -13,22 +12,24 @@ import got, { HTTPError } from 'got';
 import { defaultMetadata, endpoint } from './constant';
 import { twilioSmsConfigGuard, TwilioSmsConfig, PublicParameters } from './types';
 
-export default class TwilioSmsConnector implements SmsConnector {
+export default class TwilioSmsConnector implements SmsConnector<TwilioSmsConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
 
-  constructor(public readonly getConfig: GetConnectorConfig<TwilioSmsConfig>) {}
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is TwilioSmsConfig {
     const result = twilioSmsConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public sendMessage: EmailSendMessageFunction = async (address, type, data) => {
     const config = await this.getConfig(this.metadata.id);
-    await this.validateConfig(config);
+
+    this.validateConfig(config);
+
     const { accountSID, authToken, fromMessagingServiceSID, templates } = config;
     const template = templates.find((template) => template.usageType === type);
 
diff --git a/packages/connector-types/src/index.ts b/packages/connector-types/src/index.ts
index c6a723dfb..10d9f6416 100644
--- a/packages/connector-types/src/index.ts
+++ b/packages/connector-types/src/index.ts
@@ -80,26 +80,26 @@ export type SmsSendMessageFunction<T = unknown> = (
   config?: Record<string, unknown>
 ) => Promise<T>;
 
-export interface BaseConnector {
+export interface BaseConnector<T = unknown> {
   metadata: ConnectorMetadata;
-  validateConfig: ValidateConfig;
   getConfig: GetConnectorConfig;
+  validateConfig: ValidateConfig<T>;
 }
 
-export interface SmsConnector extends BaseConnector {
+export interface SmsConnector<T = unknown> extends BaseConnector<T> {
   sendMessage: SmsSendMessageFunction;
 }
 
-export interface EmailConnector extends BaseConnector {
+export interface EmailConnector<T = unknown> extends BaseConnector<T> {
   sendMessage: EmailSendMessageFunction;
 }
 
-export interface SocialConnector extends BaseConnector {
+export interface SocialConnector<T = unknown> extends BaseConnector<T> {
   getAuthorizationUri: GetAuthorizationUri;
   getUserInfo: GetUserInfo;
 }
 
-export type ValidateConfig<T = Record<string, unknown>> = (config: T) => Promise<void>;
+export type ValidateConfig<T = unknown> = (config: unknown) => asserts config is T;
 
 export type GetAuthorizationUri = (payload: {
   state: string;
@@ -110,7 +110,7 @@ export type GetUserInfo = (
   data: unknown
 ) => Promise<{ id: string } & Record<string, string | undefined>>;
 
-export type GetConnectorConfig<T = Record<string, unknown>> = (id: string) => Promise<T>;
+export type GetConnectorConfig = (id: string) => Promise<unknown>;
 
 export const codeDataGuard = z.object({
   code: z.string(),
diff --git a/packages/connector-wechat-native/src/index.test.ts b/packages/connector-wechat-native/src/index.test.ts
index 60dd09c3d..bffa3286e 100644
--- a/packages/connector-wechat-native/src/index.test.ts
+++ b/packages/connector-wechat-native/src/index.test.ts
@@ -1,12 +1,16 @@
-import { ConnectorError, ConnectorErrorCodes, GetConnectorConfig } from '@logto/connector-types';
+import {
+  ConnectorError,
+  ConnectorErrorCodes,
+  GetConnectorConfig,
+  ValidateConfig,
+} from '@logto/connector-types';
 import nock from 'nock';
 
 import WechatNativeConnector from '.';
 import { accessTokenEndpoint, authorizationEndpoint, userInfoEndpoint } from './constant';
 import { mockedConfig } from './mock';
-import { WechatNativeConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<WechatNativeConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const wechatNativeMethods = new WechatNativeConnector(getConnectorConfig);
 
@@ -92,16 +96,30 @@ describe('getAccessToken', () => {
 });
 
 describe('validateConfig', () => {
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
   it('should pass on valid config', async () => {
-    await expect(
-      wechatNativeMethods.validateConfig({ appId: 'appId', appSecret: 'appSecret' })
-    ).resolves.not.toThrow();
+    const validator: ValidateConfig = wechatNativeMethods.validateConfig;
+    expect(() => {
+      validator({ appId: 'appId', appSecret: 'appSecret' });
+    }).not.toThrow();
   });
-  it('should throw on empty config', async () => {
-    await expect(wechatNativeMethods.validateConfig({})).rejects.toThrowError();
+
+  it('should fail on empty config', async () => {
+    const validator: ValidateConfig = wechatNativeMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
-  it('should throw when missing appSecret', async () => {
-    await expect(wechatNativeMethods.validateConfig({ appId: 'appId' })).rejects.toThrowError();
+
+  it('should fail when missing appSecret', async () => {
+    const validator: ValidateConfig = wechatNativeMethods.validateConfig;
+    expect(() => {
+      validator({ appId: 'appId' });
+    }).toThrow();
   });
 });
 
diff --git a/packages/connector-wechat-native/src/index.ts b/packages/connector-wechat-native/src/index.ts
index 8e5204ab9..bf50213f8 100644
--- a/packages/connector-wechat-native/src/index.ts
+++ b/packages/connector-wechat-native/src/index.ts
@@ -6,7 +6,6 @@
 import {
   ConnectorMetadata,
   GetAuthorizationUri,
-  ValidateConfig,
   GetUserInfo,
   ConnectorError,
   ConnectorErrorCodes,
@@ -35,21 +34,25 @@ import {
   WechatNativeConfig,
 } from './types';
 
-export default class WechatNativeConnector implements SocialConnector {
+export default class WechatNativeConnector implements SocialConnector<WechatNativeConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
 
-  constructor(public readonly getConfig: GetConnectorConfig<WechatNativeConfig>) {}
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is WechatNativeConfig {
     const result = wechatNativeConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public getAuthorizationUri: GetAuthorizationUri = async ({ state }) => {
-    const { appId, universalLinks } = await this.getConfig(this.metadata.id);
+    const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
+    const { appId, universalLinks } = config;
 
     const queryParameters = new URLSearchParams({
       app_id: appId,
@@ -65,7 +68,11 @@ export default class WechatNativeConnector implements SocialConnector {
   public getAccessToken = async (
     code: string
   ): Promise<{ accessToken: string; openid: string }> => {
-    const { appId: appid, appSecret: secret } = await this.getConfig(this.metadata.id);
+    const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
+    const { appId: appid, appSecret: secret } = config;
 
     const httpResponse = await got.get(accessTokenEndpoint, {
       searchParams: { appid, secret, code, grant_type: 'authorization_code' },
diff --git a/packages/connector-wechat/src/index.test.ts b/packages/connector-wechat/src/index.test.ts
index 05376b446..c4539899c 100644
--- a/packages/connector-wechat/src/index.test.ts
+++ b/packages/connector-wechat/src/index.test.ts
@@ -1,12 +1,16 @@
-import { ConnectorError, ConnectorErrorCodes, GetConnectorConfig } from '@logto/connector-types';
+import {
+  ConnectorError,
+  ConnectorErrorCodes,
+  GetConnectorConfig,
+  ValidateConfig,
+} from '@logto/connector-types';
 import nock from 'nock';
 
 import WechatConnector from '.';
 import { accessTokenEndpoint, authorizationEndpoint, userInfoEndpoint } from './constant';
 import { mockedConfig } from './mock';
-import { WechatConfig } from './types';
 
-const getConnectorConfig = jest.fn() as GetConnectorConfig<WechatConfig>;
+const getConnectorConfig = jest.fn() as GetConnectorConfig;
 
 const wechatMethods = new WechatConnector(getConnectorConfig);
 
@@ -92,16 +96,30 @@ describe('getAccessToken', () => {
 });
 
 describe('validateConfig', () => {
+  /**
+   * Assertion functions always need explicit annotations.
+   * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+   */
+
   it('should pass on valid config', async () => {
-    await expect(
-      wechatMethods.validateConfig({ appId: 'appId', appSecret: 'appSecret' })
-    ).resolves.not.toThrow();
+    const validator: ValidateConfig = wechatMethods.validateConfig;
+    expect(() => {
+      validator({ appId: 'appId', appSecret: 'appSecret' });
+    }).not.toThrow();
   });
-  it('should throw on empty config', async () => {
-    await expect(wechatMethods.validateConfig({})).rejects.toThrowError();
+
+  it('should fail on empty config', async () => {
+    const validator: ValidateConfig = wechatMethods.validateConfig;
+    expect(() => {
+      validator({});
+    }).toThrow();
   });
-  it('should throw when missing appSecret', async () => {
-    await expect(wechatMethods.validateConfig({ appId: 'appId' })).rejects.toThrowError();
+
+  it('should fail when missing appSecret', async () => {
+    const validator: ValidateConfig = wechatMethods.validateConfig;
+    expect(() => {
+      validator({ appId: 'appId' });
+    }).toThrow();
   });
 });
 
diff --git a/packages/connector-wechat/src/index.ts b/packages/connector-wechat/src/index.ts
index 51b616394..63b597c48 100644
--- a/packages/connector-wechat/src/index.ts
+++ b/packages/connector-wechat/src/index.ts
@@ -6,7 +6,6 @@
 import {
   ConnectorMetadata,
   GetAuthorizationUri,
-  ValidateConfig,
   GetUserInfo,
   ConnectorError,
   ConnectorErrorCodes,
@@ -36,21 +35,25 @@ import {
   WechatConfig,
 } from './types';
 
-export default class WechatConnector implements SocialConnector {
+export default class WechatConnector implements SocialConnector<WechatConfig> {
   public metadata: ConnectorMetadata = defaultMetadata;
 
-  constructor(public readonly getConfig: GetConnectorConfig<WechatConfig>) {}
+  constructor(public readonly getConfig: GetConnectorConfig) {}
 
-  public validateConfig: ValidateConfig = async (config: unknown) => {
+  public validateConfig(config: unknown): asserts config is WechatConfig {
     const result = wechatConfigGuard.safeParse(config);
 
     if (!result.success) {
       throw new ConnectorError(ConnectorErrorCodes.InvalidConfig, result.error);
     }
-  };
+  }
 
   public getAuthorizationUri: GetAuthorizationUri = async ({ state, redirectUri }) => {
-    const { appId } = await this.getConfig(this.metadata.id);
+    const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
+    const { appId } = config;
 
     const queryParameters = new URLSearchParams({
       appid: appId,
@@ -66,7 +69,11 @@ export default class WechatConnector implements SocialConnector {
   public getAccessToken = async (
     code: string
   ): Promise<{ accessToken: string; openid: string }> => {
-    const { appId: appid, appSecret: secret } = await this.getConfig(this.metadata.id);
+    const config = await this.getConfig(this.metadata.id);
+
+    this.validateConfig(config);
+
+    const { appId: appid, appSecret: secret } = config;
 
     const httpResponse = await got.get(accessTokenEndpoint, {
       searchParams: { appid, secret, code, grant_type: 'authorization_code' },
diff --git a/packages/core/src/connectors/utilities/index.ts b/packages/core/src/connectors/utilities/index.ts
index 707d21d1a..b710d9a58 100644
--- a/packages/core/src/connectors/utilities/index.ts
+++ b/packages/core/src/connectors/utilities/index.ts
@@ -1,14 +1,12 @@
-import { ArbitraryObject } from '@logto/schemas';
-
 import RequestError from '@/errors/RequestError';
 import { findAllConnectors } from '@/queries/connector';
 import assertThat from '@/utils/assert-that';
 
-export const getConnectorConfig = async <T extends ArbitraryObject>(id: string): Promise<T> => {
+export const getConnectorConfig = async (id: string): Promise<unknown> => {
   const connectors = await findAllConnectors();
   const connector = connectors.find((connector) => connector.id === id);
 
   assertThat(connector, new RequestError({ code: 'entity.not_found', id, status: 404 }));
 
-  return connector.config as T;
+  return connector.config;
 };
diff --git a/packages/core/src/routes/connector.ts b/packages/core/src/routes/connector.ts
index 1f66c2622..76e99de72 100644
--- a/packages/core/src/routes/connector.ts
+++ b/packages/core/src/routes/connector.ts
@@ -1,3 +1,4 @@
+import { ValidateConfig } from '@logto/connector-types';
 import { arbitraryObjectGuard, ConnectorDto, Connectors, ConnectorType } from '@logto/schemas';
 import { emailRegEx, phoneRegEx } from '@logto/shared';
 import { object, string } from 'zod';
@@ -84,14 +85,22 @@ export default function connectorRoutes<T extends AuthedRouter>(router: T) {
         params: { id },
         body: { enabled },
       } = ctx.guard;
+
+      const connectorInstance = await getConnectorInstanceById(id);
       const {
         connector: { config },
         metadata,
-        validateConfig,
-      } = await getConnectorInstanceById(id);
+      } = connectorInstance;
+
+      /**
+       * Assertion functions always need explicit annotations.
+       * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+       */
+      // eslint-disable-next-line unicorn/consistent-destructuring
+      const validator: ValidateConfig = connectorInstance.validateConfig;
 
       if (enabled) {
-        await validateConfig(config);
+        validator(config);
       }
 
       // Only allow one enabled connector for SMS and Email.
@@ -135,10 +144,19 @@ export default function connectorRoutes<T extends AuthedRouter>(router: T) {
         params: { id },
         body,
       } = ctx.guard;
-      const { metadata, validateConfig } = await getConnectorInstanceById(id);
+
+      const connectorInstance = await getConnectorInstanceById(id);
+      const { metadata } = connectorInstance;
+
+      /**
+       * Assertion functions always need explicit annotations.
+       * See https://github.com/microsoft/TypeScript/issues/36931#issuecomment-589753014
+       */
+      // eslint-disable-next-line unicorn/consistent-destructuring
+      const validator: ValidateConfig = connectorInstance.validateConfig;
 
       if (body.config) {
-        await validateConfig(body.config);
+        validator(body.config);
       }
 
       const connector = await updateConnector({ set: body, where: { id }, jsonbMode: 'replace' });
@@ -187,10 +205,6 @@ export default function connectorRoutes<T extends AuthedRouter>(router: T) {
         })
       );
 
-      if (config) {
-        await connector.validateConfig(config);
-      }
-
       await connector.sendMessage(
         subject,
         'Test',
diff --git a/packages/core/src/routes/connector.update.test.ts b/packages/core/src/routes/connector.update.test.ts
index d20e62832..e7235e38c 100644
--- a/packages/core/src/routes/connector.update.test.ts
+++ b/packages/core/src/routes/connector.update.test.ts
@@ -38,7 +38,7 @@ const getConnectorInstanceByIdPlaceHolder = jest.fn(async (connectorId: string)
     sendMessage: sendMessagePlaceHolder,
   };
 });
-const validateConfigPlaceHolder = jest.fn();
+const validateConfigPlaceHolder = jest.fn() as jest.MockedFunction<ValidateConfig>;
 const sendMessagePlaceHolder = jest.fn();
 
 jest.mock('@/queries/connector', () => ({
@@ -98,7 +98,7 @@ describe('connector PATCH routes', () => {
     });
 
     it('enables one of the social connectors (with invalid config)', async () => {
-      validateConfigPlaceHolder.mockImplementationOnce(async () => {
+      validateConfigPlaceHolder.mockImplementationOnce(() => {
         throw new ConnectorError(ConnectorErrorCodes.InvalidConfig);
       });
       getConnectorInstancesPlaceHolder.mockResolvedValueOnce([
@@ -187,7 +187,7 @@ describe('connector PATCH routes', () => {
     });
 
     it('enables one of the email/sms connectors (with invalid config)', async () => {
-      validateConfigPlaceHolder.mockImplementationOnce(async () => {
+      validateConfigPlaceHolder.mockImplementationOnce(() => {
         throw new ConnectorError(ConnectorErrorCodes.InvalidConfig);
       });
       getConnectorInstancesPlaceHolder.mockResolvedValueOnce([
@@ -247,7 +247,7 @@ describe('connector PATCH routes', () => {
     });
 
     it('config validation fails', async () => {
-      validateConfigPlaceHolder.mockImplementationOnce(async () => {
+      validateConfigPlaceHolder.mockImplementationOnce(() => {
         throw new ConnectorError(ConnectorErrorCodes.InvalidConfig);
       });
       getConnectorInstancesPlaceHolder.mockResolvedValueOnce([