diff --git a/package.json b/package.json
index 5f97d92..5606833 100644
--- a/package.json
+++ b/package.json
@@ -52,7 +52,7 @@
     "beautify-proj": "0.0.4",
     "browserify": "^12.0.1",
     "browserify-istanbul": "^0.2.1",
-    "chai": "^3.4.1",
+    "chai": "^4.0.1",
     "chai-as-promised": "^5.1.0",
     "coveralls": "^2.11.6",
     "es5-shim": "^4.4.0",