diff --git a/lib/6to5/traverse/index.js b/lib/6to5/traverse/index.js
index 86ee88f0e3..12620d6e16 100644
--- a/lib/6to5/traverse/index.js
+++ b/lib/6to5/traverse/index.js
@@ -18,7 +18,7 @@ function traverse(parent, callbacks, opts) {
 
   // unknown node type to traverse
   var keys = t.VISITOR_KEYS[parent.type];
-  if (!keys) throw new Error("unknown node " + parent.type);
+  if (!keys) return;
 
   opts = opts || {};
   if (_.isArray(opts)) opts = { blacklist: opts };