diff --git a/Promise.js b/Promise.js
index c8265f0..6be8961 100644
--- a/Promise.js
+++ b/Promise.js
@@ -1330,8 +1330,8 @@ object.Mixin('PromiseMixin', 'soft', {
 			// XXX should we just check for .then(..) ???
 			// XXX update README if this changes...
 			: (data.length == 1 
-					&& Symbol.asyncIterator in data[0]
-					&& 'then' in data[0]) ?
+					&& data[0][Symbol.asyncIterator]
+					&& data[0].then) ?
 				data[0].then(func, ...error)
 			: error.length > 0 ?
 				function(){
diff --git a/package.json b/package.json
index 81d45f7..3411704 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "ig-types",
-  "version": "6.24.23",
+  "version": "6.24.24",
   "description": "Generic JavaScript types and type extensions...",
   "main": "main.js",
   "scripts": {