diff --git a/package.json b/package.json
index 8f1e80c5..02947bc0 100644
--- a/package.json
+++ b/package.json
@@ -29,6 +29,7 @@
   },
   "license": "ISC",
   "dependencies": {
+    "bluebird": "^3.5.1",
     "lru-cache": "^4.1.2",
     "make-fetch-happen": "^3.0.0",
     "npm-package-arg": "^6.0.0",