diff --git a/lib/6to5/traversal/scope.js b/lib/6to5/traversal/scope.js
index 43f2dc97d3..f2f9691554 100644
--- a/lib/6to5/traversal/scope.js
+++ b/lib/6to5/traversal/scope.js
@@ -224,7 +224,10 @@ Scope.prototype.inferType = function (node) {
 
   if (t.isCallExpression(target) && t.isIdentifier(target.callee)) {
     var funcInfo = this.getBindingInfo(target.callee.name);
-    if (funcInfo) return funcInfo.node.returnType;
+    if (funcInfo) {
+      var funcNode = funcInfo.node;
+      return !funcInfo.reassigned && t.isFunction(funcNode) && node.returnType;
+    }
   }
 
   if (t.isIdentifier(target)) {