diff --git a/lib/preprocessor.js b/lib/preprocessor.js
index c27a7ee..4e88771 100644
--- a/lib/preprocessor.js
+++ b/lib/preprocessor.js
@@ -4,7 +4,7 @@ var istanbul  = require('istanbul'),
 
 var createCoveragePreprocessor = function(logger, basePath, reporters, coverageReporter) {
   var log = logger.create('preprocessor.coverage');
-  var instrumenterOverrides = coverageReporter.instrumenter || {};
+  var instrumenterOverrides = (coverageReporter && coverageReporter.instrumenter) || {};
   var instrumenters = {istanbul: istanbul, ibrik: ibrik};
 
   // if coverage reporter is not used, do not preprocess the files