diff --git a/packages/actions/src/runtime/route.ts b/packages/actions/src/runtime/route.ts
index 068203a7bb..73c72f391d 100644
--- a/packages/actions/src/runtime/route.ts
+++ b/packages/actions/src/runtime/route.ts
@@ -10,13 +10,14 @@ export const POST: APIRoute = async (context) => {
 	const actionPathKeys = url.pathname.replace('/_actions/', '').split('.');
 	const action = await getAction(actionPathKeys);
 	const contentType = request.headers.get('Content-Type');
-	let args: any;
-	if (contentType === 'application/json') {
-		args = await request.clone().json();
-	}
-	if (formContentTypes.some((f) => contentType?.startsWith(f))) {
-		args = await request.clone().formData();
+	if (contentType !== 'application/json') {
+		throw new ActionError({
+			status: 'INTERNAL_SERVER_ERROR',
+			message:
+				'Called an action with a non-JSON body. To enhance an action to accept form data, add `enhance: true` to your `defineAction()` config.',
+		});
 	}
+	const args = await request.clone().json();
 	let result: unknown;
 	try {
 		result = await ApiContextStorage.run(context, () => action(args));