diff --git a/package.json b/package.json
index 836220c..239de25 100644
--- a/package.json
+++ b/package.json
@@ -25,7 +25,7 @@
     "minimist": "1.2.0"
   },
   "devDependencies": {
-    "chai": "^3.4.1",
+    "chai": "^4.0.0",
     "eslint": "^2.0.0",
     "eslint-config-standard": "^5.1.0",
     "eslint-plugin-promise": "^1.0.8",