diff --git a/lib/6to5/types/index.js b/lib/6to5/types/index.js
index a3bbd5e55f..21aa975630 100644
--- a/lib/6to5/types/index.js
+++ b/lib/6to5/types/index.js
@@ -238,10 +238,21 @@ t.isReferenced = function (node, parent) {
     return parent.key === node && parent.computed;
   }
 
+  if (t.isRestElement(parent)) {
+    return false;
+  }
+
+  if (t.isAssignmentPattern(parent)) {
+    return parent.right !== node;
+  }
+
+  if (t.isPattern(parent)) {
+    return false;
+  }
+
   if (t.isFunction(parent)) {
     for (var i = 0; i < parent.params.length; i++) {
       var param = parent.params[i];
-      if (t.isRestElement(param)) param = param.argument;
       if (param === node) return false;
     }