diff --git a/package.json b/package.json
index c1d27cd..a4367fa 100644
--- a/package.json
+++ b/package.json
@@ -39,7 +39,7 @@
     "esprima": "^3.1.3"
   },
   "devDependencies": {
-    "chai": "^3.4.0",
+    "chai": "^4.1.1",
     "eslint": "^3.17.1",
     "mocha": "^3.2.0"
   },