diff --git a/lib/config.js b/lib/config.js
index f6b17453..0859ee50 100644
--- a/lib/config.js
+++ b/lib/config.js
@@ -202,7 +202,7 @@ function preprocessConfig(cfg) {
     var root = cfg.http["root-domain"];
     root = root.replace(/^\.*/, "");
     cfg.http["root-domain"] = root;
-    if (root.indexOf(".") !== -1) {
+    if (root.indexOf(".") !== -1 && !net.isIP(root)) {
         root = "." + root;
     }
     cfg.http["root-domain-dotted"] = root;