diff --git a/packages/runtime-vapor/src/directive.ts b/packages/runtime-vapor/src/directive.ts
index ad6072b4f..3c796d910 100644
--- a/packages/runtime-vapor/src/directive.ts
+++ b/packages/runtime-vapor/src/directive.ts
@@ -99,6 +99,7 @@ export function withDirectives<T extends Node>(
 
     // register source
     if (source) {
+      // callback will be overridden by middleware
       renderWatch(source, NOOP)
     }
   }