diff --git a/node_modules/c9/urls.js b/node_modules/c9/urls.js
index 4b0c12ee..429ba8e2 100644
--- a/node_modules/c9/urls.js
+++ b/node_modules/c9/urls.js
@@ -26,8 +26,8 @@ function main(options, imports, register) {
  * Get a desired base URL, given some context.
  * 
  * @param req                             The current request object or URL
- * @param {String} sourceUrlPattern       The source URL pattern, e.g. https://ide.$DOMAIN
- * @param {String} [targetBaseUrlPattern] The target URL pattern, e.g. https://$DOMAIN
+ * @param {String} [sourceUrlPattern]     The source URL pattern, e.g. https://ide.$DOMAIN
+ * @param {String} targetBaseUrlPattern   The target URL pattern, e.g. https://$DOMAIN
  */
 plugin.getBaseUrl = function(req, sourceBaseUrlPattern, targetBaseUrlPattern) {
     var sourceHost = req.headers && req.headers.host
@@ -39,15 +39,20 @@ plugin.getBaseUrl = function(req, sourceBaseUrlPattern, targetBaseUrlPattern) {
         .replace(/\/.*/, "")
         .replace("$DOMAIN", "([^/]+)");
     var hostMatch = sourceHost.match(sourceHostMatcher);
-    if (!hostMatch) {
+    var targetHost;
+    if (hostMatch) {
+        targetHost = hostMatch[1];
+    }
+    else {
         errorLogger.log(new Error("Could not construct URL: request host "
             + sourceHost + " should match " + sourceBaseUrlPattern));
-        return replaceDomain(targetBaseUrlPattern || sourceBaseUrlPattern, "c9.io")
-            .replace(/\/$/, "");
+        targetHost = "c9.io";
     }
     
-    return replaceDomain(targetBaseUrlPattern || sourceBaseUrlPattern, hostMatch[1])
-        .replace(/\/$/, "");;
+    if (targetHost.match(/^(ide|vfs)./) && !targetBaseUrlPattern)
+        errorLogger.log(new Error("Warning: no targetBaseUrlPattern specified, will stay at " + targetHost), { sourceBaseUrlPattern: sourceBaseUrlPattern });
+    return replaceDomain(targetBaseUrlPattern || sourceBaseUrlPattern, targetHost)
+        .replace(/\/$/, "");
 };
 
 plugin.replaceDomains = function(settings, domains) {