diff --git a/package.json b/package.json
index ac3d363..39d5139 100644
--- a/package.json
+++ b/package.json
@@ -20,7 +20,8 @@
     "ava": "^0.19.0",
     "babel-cli": "^6.24.1",
     "babel-preset-env": "^1.3.3",
-    "babel-register": "^6.24.1"
+    "babel-register": "^6.24.1",
+    "sinon": "^2.1.0"
   },
   "ava": {
     "require": [