diff --git a/src/adapter.js b/src/adapter.js
index <HASH>..<HASH> 100644
--- a/src/adapter.js
+++ b/src/adapter.js
@@ -80,7 +80,7 @@ var createMochaReporterConstructor = function(tc) {
 
 var createMochaStartFn = function(mocha) {
   return function(config) {
-    if(config.grep){
+    if(config && config.grep){
       mocha.grep(config.grep);
     }
     mocha.run();
fix: config does not have to be defined

This is a fix for bug introduced in 9bdcae<I>f<I>cdcee<I>ed0fb<I>dd<I>c9ce<I>ed