Never call back twice. Fixes #159.

lib/client.js

@@ -31,13 +31,35 @@ var BUCKET_OPS_MAX = 1000;
  * @param {Request} req The http request
  * @param {Function} fn(err, res) The callback function.
  * err - The exception if an exception occurred while sending the http
- * request (for example if internet connection was lost).
+ *       request (for example if internet connection was lost).
  * res - The http response if no exception occurred.
  * @api private
  */
 function registerReqListeners(req, fn){
-  req.on('response', function(res){ fn(null, res); });
-  req.on('error', fn);
+  var hasCalledBack = false;
+
+  function cleanup() {
+    hasCalledBack = true;
+    req.removeListener('response', onResponse);
+    req.removeListener('error', onError);
+  }
+
+  function onResponse(res){
+    if (!hasCalledBack) {
+      fn(null, res);
+    }
+    cleanup();
+  }
+
+  function onError(err){
+    if (!hasCalledBack) {
+      fn(err);
+    }
+    cleanup();
+  }
+
+  req.on('response', onResponse);
+  req.on('error', onError);
 }
 
 function ensureLeadingSlash(filename) {