diff --git a/package.json b/package.json
index 6c22545..f088f67 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,8 @@
     "lodash": "^3.10.1",
     "pluralize": "^1.2.1",
     "roots-util": "0.1.x",
-    "string": "^3.1.3"
+    "string": "^3.1.3",
+    "when": "^3.7.5"
   },
   "devDependencies": {
     "ava": "^0.7.0",