diff --git a/package.json b/package.json
index d35996f..a964fe2 100644
--- a/package.json
+++ b/package.json
@@ -40,7 +40,7 @@
     "underscore": "^1.8.3"
   },
   "devDependencies": {
-    "chai": "^3.5.0",
+    "chai": "^4.3.4",
     "mocha": "^3.1.2",
     "mockery": "^2.0.0",
     "sinon": "^2.1.0",