diff --git a/package.json b/package.json
index e799b0b..cbf3577 100644
--- a/package.json
+++ b/package.json
@@ -20,7 +20,7 @@
   "author": "Vojta Jina <vojta.jina@gmail.com>",
   "dependencies": {},
   "devDependencies": {
-    "chai": "^3.3.0",
+    "chai": "^4.0.0",
     "eslint": "^1.6.0",
     "eslint-config-standard": "^4.4.0",
     "eslint-plugin-standard": "^1.3.1",