diff --git a/lib/6to5/transformation/transformers/es6/parameters.default.js b/lib/6to5/transformation/transformers/es6/parameters.default.js
index 7e7d9ac5a4..f5a393fef2 100644
--- a/lib/6to5/transformation/transformers/es6/parameters.default.js
+++ b/lib/6to5/transformation/transformers/es6/parameters.default.js
@@ -16,10 +16,12 @@ var hasDefaults = function (node) {
 
 var iifeVisitor = {
   enter: function (node, parent, scope, state) {
-    if (t.isReferencedIdentifier(node, parent) && state.scope.hasOwnReference(node.name)) {
-      state.iife = true;
-      this.stop();
-    }
+    if (!t.isReferencedIdentifier(node, parent)) return;
+    if (!state.scope.hasOwnBinding(node.name)) return;
+    if (state.scope.bindingEquals(node.name, node)) return;
+
+    state.iife = true;
+    this.stop();
   }
 };