diff --git a/package.json b/package.json
index 528d0ee..912d9d4 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,7 @@
   },
   "devDependencies": {
     "bootprint": "^1.0.0",
-    "chai": "^3.5.0",
+    "chai": "^4.0.1",
     "ghooks": "^2.0.0",
     "m-io": "^0.5.0",
     "mocha": "^3.2.0",