diff --git a/packages/open-next/src/core/routingHandler.ts b/packages/open-next/src/core/routingHandler.ts
index 54936d66..1c4e7263 100644
--- a/packages/open-next/src/core/routingHandler.ts
+++ b/packages/open-next/src/core/routingHandler.ts
@@ -34,6 +34,11 @@ const optionalBasepathPrefixRegex = !!RoutesManifest.basePath
   ? `^${RoutesManifest.basePath}/?`
   : "^/";
 
+// Add the basePath prefix to the api routes
+const apiPrefix = !!RoutesManifest.basePath
+  ? `${RoutesManifest.basePath}/api`
+  : "/api";
+
 const staticRegexp = RoutesManifest.routes.static.map(
   (route) =>
     new RegExp(
@@ -145,8 +150,8 @@ export default async function routingHandler(
   // /api even if it's a page route doesn't get generated in the manifest
   // Ideally we would need to properly check api routes here
   const isApiRoute =
-    internalEvent.rawPath === "/api" ||
-    internalEvent.rawPath.startsWith("/api/");
+    internalEvent.rawPath === apiPrefix ||
+    internalEvent.rawPath.startsWith(`${apiPrefix}/`);
 
   const isNextImageRoute = internalEvent.rawPath.startsWith("/_next/image");