diff --git a/f8/coroutine.cc b/f8/coroutine.cc
index 01679c4..a094bcb 100644
--- a/f8/coroutine.cc
+++ b/f8/coroutine.cc
@@ -97,9 +97,10 @@ namespace f8
         return awaiter->GetResult();
     }
 
-    std::shared_ptr<a8::Results> Coroutine::CoAwait(std::function<(std::shared_ptr<a8::Awaiter>)> cb)
+    std::shared_ptr<a8::Results> Coroutine::CoAwait
+    (std::function<void (std::shared_ptr<a8::Awaiter>)> cb)
     {
-
+        return CoAwait(std::make_shared<a8::CbPromise>(cb));
     }
 
     void Coroutine::Attach()
diff --git a/f8/coroutine.h b/f8/coroutine.h
index 6ca251f..2ba5846 100644
--- a/f8/coroutine.h
+++ b/f8/coroutine.h
@@ -19,7 +19,8 @@ namespace f8
         void CoResume();
         void CoYield();
         std::shared_ptr<a8::Results> CoAwait(std::shared_ptr<a8::Awaiter> awaiter);
-        std::shared_ptr<a8::Results> CoAwait(std::function<(std::shared_ptr<a8::Awaiter>)> cb);
+        std::shared_ptr<a8::Results> CoAwait
+        (std::function<void (std::shared_ptr<a8::Awaiter>)> cb);
         std::shared_ptr<a8::Awaiter> Sleep(long long time);
 
     private: