diff --git a/package.json b/package.json
index 7a8c533..6fe037b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "greenlock",
-  "version": "2.2.16",
+  "version": "2.2.17",
   "description": "Let's Encrypt for node.js on npm",
   "main": "index.js",
   "scripts": {
@@ -58,7 +58,8 @@
     "request": "^2.75.0"
   },
   "optionalDependencies": {
-    "bluebird": "^3.5.1"
+    "bluebird": "^3.5.1",
+    "le-acme-core": "^2.1.3"
   },
   "dependencies": {
     "acme-v2": "^1.0.6",