diff --git a/package.json b/package.json
index 96a01d4..d4de564 100644
--- a/package.json
+++ b/package.json
@@ -52,7 +52,7 @@
   },
   "devDependencies": {
     "mocha": "~3.3.0",
-    "chai": "~3.5.0",
+    "chai": "~4.0.0",
     "grunt": "~1.0.1",
     "grunt-mocha-test": "~0.13.0",
     "grunt-contrib-watch": "~1.0.0",