diff --git a/packages/builder/src/builder.js b/packages/builder/src/builder.js
index d0dfe27124..72d59adadf 100644
--- a/packages/builder/src/builder.js
+++ b/packages/builder/src/builder.js
@@ -414,7 +414,7 @@ export default class Builder {
     // router.extendRoutes method
     if (typeof this.options.router.extendRoutes === 'function') {
       // let the user extend the routes
-      const extendedRoutes = this.options.router.extendRoutes(
+      const extendedRoutes = await this.options.router.extendRoutes(
         templateVars.router.routes,
         r
       )