diff --git a/package.json b/package.json
index 3726cf7..a55d787 100644
--- a/package.json
+++ b/package.json
@@ -10,7 +10,7 @@
   },
   "devDependencies": {
     "bluebird": "2",
-    "istanbul": "0",
+    "istanbul": "0.4.2",
     "mocha": "2"
   },
   "scripts": {