diff --git a/node.js b/node.js
index fe6de54..7827f75 100644
--- a/node.js
+++ b/node.js
@@ -43,6 +43,23 @@ function create(deps) {
   };
 
   RSA.generateKeypair = function (length, exponent, options, cb) {
+    if (!RSA._URSA && /arm|mips/i.test(require('os').arch) && !RSA._SLOW_WARN) {
+      console.warn("================================================================");
+      console.warn("                         WARNING");
+      console.warn("================================================================");
+      console.warn("");
+      console.warn("WARNING: You are generating an RSA key using pure JavaScript on");
+      console.warn("         a VERY SLOW cpu. This could take DOZENS of minutes!");
+      console.warn("");
+      console.warn("         We recommend installing a C compiler and 'ursa'");
+      console.warn("");
+      console.warn("EXAMPLE:");
+      console.warn("");
+      console.warn("        sudo apt-get install build-essential && npm install ursa");
+      console.warn("");
+      console.warn("================================================================");
+      RSA._SLOW_WARN = true;
+    }
     var keypair = {
       privateKeyPem: undefined
     , publicKeyPem: undefined