diff --git a/package.json b/package.json
index a556b67..84fd150 100644
--- a/package.json
+++ b/package.json
@@ -31,7 +31,7 @@
     "babel-polyfill": "^6.6.1",
     "babel-preset-es2015": "^6.6.0",
     "babelify": "^7.2.0",
-    "chai": "^3.5.0",
+    "chai": "^4.0.0",
     "eslint": "^2.7.0",
     "grunt": "^1.0.1",
     "grunt-babel": "^6.0.0",