diff --git a/package.json b/package.json
index be14c80f..82e7f042 100644
--- a/package.json
+++ b/package.json
@@ -71,7 +71,7 @@
   },
   "devDependencies": {
     "broccoli-asset-rev": "^2.4.5",
-    "chai": "^3.5.0",
+    "chai": "^4.0.2",
     "cssnano": "^3.9.1",
     "cssstats": "^3.0.0",
     "del-cli": "^0.2.1",