diff --git a/package.json b/package.json
index 55b3c87..fa3d142 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,7 @@
   },
   "devDependencies": {
     "babel-eslint": "7.2.1",
-    "chai": "3.5.0",
+    "chai": "4.0.0",
     "chai-string": "1.3.0",
     "eslint": "3.19.0",
     "grunt-contrib-watch": "1.0.0",