diff --git a/package.json b/package.json
index bded5eb..01f6090 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,7 @@
   "repository": "math-utils/area-polygon",
   "devDependencies": {
     "mocha": "2",
-    "istanbul": "0"
+    "istanbul": "0.4.2"
   },
   "scripts": {
     "test": "mocha --reporter spec",