diff --git a/package.json b/package.json
index c3abcea..a53c792 100644
--- a/package.json
+++ b/package.json
@@ -156,7 +156,7 @@
   "devDependencies": {
     "babel-plugin-transform-es2015-modules-systemjs": "^6.6.5",
     "babel-preset-es2015": "^6.6.0",
-    "chai": "^3.2.0",
+    "chai": "^4.0.0",
     "connect-pushstate": "^1.0.0",
     "del": "^2.0.2",
     "gulp": "^3.9.1",