diff --git a/README.md b/README.md
index 0caf41d..1882aa9 100644
--- a/README.md
+++ b/README.md
@@ -14,11 +14,28 @@ This is useful for **certbot** and **letsencrypt**.
 Install
 =======
 
-```
-# node.js
-npm install --save rsa-compat
+node.js
 
-# CLI
+```bash
+npm install --save rsa-compat
+```
+
+For **more efficient** RSA key generation:
+<small>(I dropped `ursa` as an "optional dependency" because the non-fatal error messages on unsupported platforms and node versions were confusing people, but I still recommend installing it)</small>
+
+```bash
+npm install --save ursa
+```
+
+**Node &lt; v6** support:
+
+```bash
+npm install --save buffer-v6-polyfill
+```
+
+### CLI
+
+```bash
 npm install --global rsa-compat
 ```
 
@@ -211,3 +228,9 @@ var web64 = RSA.generateCsrDerWeb64(keypair, [ 'example.com', 'www.example.com'
 
 console.log(web64);
 ```
+
+ChangeLog:
+
+* v1.4.0
+  * remove ursa as dependency (just causes confusion), but note in docs
+  * drop node &lt; v6 support
diff --git a/node.js b/node.js
index 442b753..464fced 100644
--- a/node.js
+++ b/node.js
@@ -5,7 +5,11 @@
 */
 'use strict';
 
-require('buffer-v6-polyfill');
+try {
+  require('buffer-v6-polyfill');
+} catch(e) {
+  /* ignore */
+}
 
 var RSA = {};
 var NOBJ = {};
diff --git a/package.json b/package.json
index d9fd971..7f6525b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "rsa-compat",
-  "version": "1.3.2",
+  "version": "1.4.0",
   "description": "RSA utils that work on Windows, Mac, and Linux with or without C compiler",
   "main": "node.js",
   "bin": {
@@ -39,10 +39,10 @@
   },
   "homepage": "https://git.coolaj86.com/coolaj86/rsa-compat.js#readme",
   "dependencies": {
-    "buffer-v6-polyfill": "^1.0.3",
     "node-forge": "^0.6.41"
   },
-  "optionalDependencies": {
+  "trulyOptionalDependencies": {
+    "buffer-v6-polyfill": "^1.0.3",
     "ursa": "^0.9.4"
   }
 }