diff --git a/index.js b/index.js
index 45add6e..1ea0328 100644
--- a/index.js
+++ b/index.js
@@ -393,6 +393,9 @@ Greenlock.create = function (gl) {
           if (!gl.approvedDomains.length) {
             throw new Error("le-sni-auto is not properly configured. Missing approveDomains(domain, certs, callback)");
           }
+          if (!/[a-z]/i.test(lexOpts.domain)) {
+            throw new Error("le-sni-auto does not allow IP addresses by default");
+          }
 
           if (!Array.isArray(gl.approvedDomains)) {
             // The acme-v2 package uses pre-flight test challenges to
diff --git a/package.json b/package.json
index a39f3be..c7c81c3 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "greenlock",
-  "version": "2.6.4",
+  "version": "2.6.5",
   "description": "Let's Encrypt for node.js on npm",
   "main": "index.js",
   "files": [