diff --git a/lib/6to5/types/index.js b/lib/6to5/types/index.js
index 31533075e7..9ba1beafa6 100644
--- a/lib/6to5/types/index.js
+++ b/lib/6to5/types/index.js
@@ -117,7 +117,7 @@ t.getIds = function (node) {
       search = search.concat(id.declarations);
     } else if (t.isVariableDeclarator(id)) {
       search.push(id.id);
-    } else {
+    } else if (id) {
       throw new Error("unknown node " + id.type);
     }
   }