diff --git a/package.json b/package.json
index b76c826..a6f889d 100644
--- a/package.json
+++ b/package.json
@@ -17,7 +17,7 @@
     "ws": "^2.3.1"
   },
   "devDependencies": {
-    "chai": "^3.5.0",
+    "chai": "^4.0.0",
     "coffee-script": "^1.12.5",
     "fbp": "^1.5.0",
     "mocha": "^3.2.0",