diff --git a/README.md b/README.md
index 60b8182..84fa5b5 100644
--- a/README.md
+++ b/README.md
@@ -74,19 +74,17 @@ Install
 npm install --save greenlock@2.x
 ```
 
-<small>
 **Optional** dependency for *more efficient* RSA key generation:
+<small>(important for those on ARM devices like Raspberry Pi)</small>
 ```bash
 npm install --save ursa
 ```
-(important for those on ARM devices like Raspberry Pi)
 
 **Optional** dependency for *Let's Encrypt v01* (pre-draft ACME spec) compatibility:
+<small>(important for those on ARM devices like Raspberry Pi)</small>
 ```bash
 npm install --save le-acme-core
 ```
-(important for those on ARM devices like Raspberry Pi)
-</small>
 
 
 ### Production vs Staging
diff --git a/index.js b/index.js
index dbb5a45..8f607e5 100644
--- a/index.js
+++ b/index.js
@@ -3,6 +3,12 @@
 var DAY = 24 * 60 * 60 * 1000;
 //var MIN = 60 * 1000;
 var ACME = require('acme-v2/compat').ACME;
+var PromiseA;
+try {
+  PromiseA = require('bluebird');
+} catch(e) {
+  PromiseA = global.Promise;
+}
 
 var Greenlock = module.exports;
 Greenlock.Greenlock = Greenlock;
@@ -70,8 +76,6 @@ Greenlock._undefine = function (gl) {
   return gl;
 };
 Greenlock.create = function (gl) {
-  var PromiseA = require('bluebird');
-
   gl.store = gl.store || require('le-store-certbot').create({
     debug: gl.debug
   , configDir: gl.configDir
diff --git a/lib/core.js b/lib/core.js
index e7e8dd5..586e1eb 100644
--- a/lib/core.js
+++ b/lib/core.js
@@ -1,5 +1,12 @@
 'use strict';
 
+var PromiseA;
+try {
+  PromiseA = require('bluebird');
+} catch(e) {
+  PromiseA = global.Promise;
+}
+
 function _log(debug) {
   if (debug) {
     var args = Array.prototype.slice.call(arguments);
@@ -10,7 +17,6 @@ function _log(debug) {
 }
 
 module.exports.create = function (gl) {
-  var PromiseA = require('bluebird');
   var utils = require('./utils');
   var RSA = PromiseA.promisifyAll(require('rsa-compat').RSA);
   var log = gl.log || _log; // allow custom log
diff --git a/package.json b/package.json
index 4027d88..9e1eae8 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "greenlock",
-  "version": "2.2.20",
+  "version": "2.3.0",
   "description": "Let's Encrypt for node.js on npm",
   "main": "index.js",
   "scripts": {
@@ -57,9 +57,10 @@
   "devDependencies": {
     "request": "^2.75.0"
   },
-  "optionalDependencies": {
+  "trulyOptionalDependencies": {
     "bluebird": "^3.5.1",
-    "le-acme-core": "^2.1.3"
+    "le-acme-core": "^2.1.3",
+    "ursa": "^0.9.4"
   },
   "dependencies": {
     "acme": "^1.0.6",
@@ -71,7 +72,7 @@
     "le-store-certbot": "^2.1.0",
     "node.extend": "^1.1.5",
     "pkijs": "^1.3.27",
-    "rsa-compat": "^1.3.2"
+    "rsa-compat": "^1.4.0"
   },
   "engines": {
     "node": ">=4.5"