diff --git a/Implab/Deferred.cs b/Implab/Deferred.cs
--- a/Implab/Deferred.cs
+++ b/Implab/Deferred.cs
@@ -36,9 +36,9 @@ namespace Implab {
 
             else if (m_dispatcher != null)
                 // dispatch (see ecma-262/6.0: 25.4.1.3.2 Promise Resolve Functions)
-                m_dispatcher.Enqueue(() => thenable.Then(this));
+                m_dispatcher.Enqueue(() => Chain(thenable));
             else
-                thenable.Then(this);
+                Chain(thenable);
         }
 
         void Chain(IPromise thenable) {
diff --git a/Implab/IResolvable.cs b/Implab/IResolvable.cs
--- a/Implab/IResolvable.cs
+++ b/Implab/IResolvable.cs
@@ -8,8 +8,6 @@ namespace Implab {
 
         void Resolve();
 
-        void Resolve(IPromise thenable);
-
         /// <summary>
         /// Reject the promise with the specified error.
         /// </summary>