diff --git a/package.json b/package.json
index c9f3c57..88b45b7 100644
--- a/package.json
+++ b/package.json
@@ -39,7 +39,7 @@
   },
   "homepage": "https://github.com/defstream/work.flow",
   "devDependencies": {
-    "chai": "3.5.0",
+    "chai": "4.0.1",
     "codecov": "1.0.1",
     "istanbul": "0.4.3",
     "mocha": "2.4.5",