diff --git a/lib/_debugger.js b/lib/_debugger.js
index 6a584ea8d38..6392b882933 100644
--- a/lib/_debugger.js
+++ b/lib/_debugger.js
@@ -127,7 +127,10 @@ exports.Client = Client;
 
 
 Client.prototype._addHandle = function(desc) {
-  if (typeof desc != 'object' || !desc.handle) throw new Error('bad type');
+  if (typeof desc != 'object' || typeof desc.handle != 'number') {
+    throw new Error('bad type');
+  }
+
   this.handles[desc.handle] = desc;
 
   if (desc.type == 'script') {