diff --git a/package.json b/package.json
index 4d45805..cd8f0b7 100644
--- a/package.json
+++ b/package.json
@@ -25,7 +25,7 @@
     "preversion": "npm run thoughtcheck"
   },
   "devDependencies": {
-    "chai": "^3.5.0",
+    "chai": "^4.0.0",
     "customize": "^1.0.0",
     "deep-aplus": "^1.0.4",
     "ghooks": "^2.0.0",