diff --git a/lib/6to5/transformation/modules/_default.js b/lib/6to5/transformation/modules/_default.js
index 64608d26d5..46c8b15af1 100644
--- a/lib/6to5/transformation/modules/_default.js
+++ b/lib/6to5/transformation/modules/_default.js
@@ -52,8 +52,7 @@ DefaultFormatter.prototype.checkCollisions = function () {
   var file = this.file;
 
   var isLocalReference = function (node, scope) {
-    var localImport = localImports[node.name];
-    return t.isIdentifier(node) && localImport && localImport !== node;
+    return t.isIdentifier(node) && _.has(localImports, node.name) && localImports[node.name] !== node;
   };
 
   var check = function (node) {