diff --git a/Implab/Parallels/ArrayTraits.cs b/Implab/Parallels/ArrayTraits.cs
--- a/Implab/Parallels/ArrayTraits.cs
+++ b/Implab/Parallels/ArrayTraits.cs
@@ -133,6 +133,9 @@ namespace Implab.Parallels {
             if (threads <= 0)
                 throw new ArgumentOutOfRangeException("Threads number must be greater then zero");
 
+            if (source.Length == 0)
+                return Promise<TDst[]>.ResultToPromise(new TDst[0]);
+
             var promise = new Promise<TDst[]>();
             var res = new TDst[source.Length];
             var pending = source.Length;
diff --git a/Implab/Promise.cs b/Implab/Promise.cs
--- a/Implab/Promise.cs
+++ b/Implab/Promise.cs
@@ -236,7 +236,7 @@ namespace Implab {
 
         public IPromiseBase Then(Action success)
         {
-            return Then(success);
+            return Then(x => success());
         }
 
         /// <summary>