diff --git a/package.json b/package.json
index 2323afd..eae81f6 100644
--- a/package.json
+++ b/package.json
@@ -30,7 +30,7 @@
     "test": "mocha"
   },
   "devDependencies": {
-    "chai": "^3.5.0",
+    "chai": "^4.0.1",
     "mocha": "^3.2.0"
   }
 }