diff --git a/package.json b/package.json
index a169635..c6a1837 100644
--- a/package.json
+++ b/package.json
@@ -22,7 +22,7 @@
   "license": "MIT",
   "devDependencies": {
     "babel-preset-es2015": "^6.3.13",
-    "chai": "^3.4.1",
+    "chai": "^4.0.2",
     "eslint": "^3.10.2",
     "gulp": "^3.9.0",
     "gulp-babel": "^6.1.1",