diff --git a/package.json b/package.json
index dde6388..8f91ec6 100644
--- a/package.json
+++ b/package.json
@@ -11,7 +11,7 @@
   "author": "Martin Colwell",
   "license": "ISC",
   "devDependencies": {
-    "chai": "^3.5.0",
+    "chai": "^4.0.1",
     "istanbul": "^0.4.2",
     "lodash": "^4.7.0",
     "mocha": "^2.4.5"