diff --git a/package.json b/package.json
index bf6a42f..2fd32c0 100644
--- a/package.json
+++ b/package.json
@@ -29,6 +29,7 @@
   },
   "devDependencies": {
     "chai": "^3.5.0",
+    "chai-as-promised": "^6.0.0",
     "codecov": "^1.0.1",
     "istanbul": "^0.4.5",
     "mocha": "^3.2.0"