diff --git a/lib/6to5/transformation/transformers/es6/constants.js b/lib/6to5/transformation/transformers/es6/constants.js
index 1030a290ec..394bf7a49d 100644
--- a/lib/6to5/transformation/transformers/es6/constants.js
+++ b/lib/6to5/transformation/transformers/es6/constants.js
@@ -6,7 +6,7 @@ var t        = require("../../../types");
 var visitor = {
   enter: function (node, parent, scope, context, state) {
     if (t.isDeclaration(node) || t.isAssignmentExpression(node)) {
-      var ids = t.getDeclarations(node);
+      var ids = t.getBindingIdentifiers(node);
 
       for (var key in ids) {
         var id = ids[key];
@@ -21,6 +21,9 @@ var visitor = {
         // constant so we can just ignore it
         if (id === constant) continue;
 
+        var localBinding = scope.get(key, true);
+        if (localBinding !== constant) continue;
+
         throw state.file.errorWithNode(id, key + " is read-only");
       }
     } else if (t.isScope(node)) {