diff --git a/package.json b/package.json
index afe07c5..d94acad 100644
--- a/package.json
+++ b/package.json
@@ -32,7 +32,7 @@
     "openpgp": "^2.3.0"
   },
   "devDependencies": {
-    "chai": "^3.5.0",
+    "chai": "^4.1.1",
     "co-mocha": "^1.1.2",
     "jscs": "^3.0.7",
     "jshint": "^2.9.4",