diff --git a/.changeset/large-waves-cheat.md b/.changeset/large-waves-cheat.md
new file mode 100644
index 0000000000..bd61307b3d
--- /dev/null
+++ b/.changeset/large-waves-cheat.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes a bug that caused some dev server asset requests to return 404 when trailingSlash was set to "always"
diff --git a/packages/astro/src/vite-plugin-astro-server/trailing-slash.ts b/packages/astro/src/vite-plugin-astro-server/trailing-slash.ts
index fff8d31178..1872214cfe 100644
--- a/packages/astro/src/vite-plugin-astro-server/trailing-slash.ts
+++ b/packages/astro/src/vite-plugin-astro-server/trailing-slash.ts
@@ -22,6 +22,9 @@ export function trailingSlashMiddleware(settings: AstroSettings): vite.Connect.N
 			/* malformed uri */
 			return next(e);
 		}
+		if(pathname.startsWith('/_') || pathname.startsWith('/@')) {
+			return next();
+		}
 		if (
 			(trailingSlash === 'never' && pathname.endsWith('/') && pathname !== '/') ||
 			(trailingSlash === 'always' && !pathname.endsWith('/') && !hasFileExtension(pathname))
diff --git a/packages/astro/test/ssr-error-pages.test.js b/packages/astro/test/ssr-error-pages.test.js
index 61335574d2..0ffb7ddbd7 100644
--- a/packages/astro/test/ssr-error-pages.test.js
+++ b/packages/astro/test/ssr-error-pages.test.js
@@ -169,6 +169,12 @@ describe('trailing slashes for error pages', () => {
 			const $ = cheerio.load(html);
 			assert.equal($('h1').text(), `Something went horribly wrong!`);
 		});
+
+		it('serves Vite assets correctly when trailingSlash is always', async () => {
+			const response = await fixture.fetch('/@vite/client');
+			assert.equal(response.status, 200);
+		});
+
 	});
 
 	describe('Production', () => {