diff --git a/testing/marionette/server.js b/testing/marionette/server.js
index 9ada7908620e4..ce46eb1cf5ef4 100644
--- a/testing/marionette/server.js
+++ b/testing/marionette/server.js
@@ -324,6 +324,8 @@ server.TCPListener = class {
     let flags = Ci.nsIServerSocket.KeepWhenOffline;
     if (this.forceLocal) {
       flags |= Ci.nsIServerSocket.LoopbackOnly;
+    } else {
+      logger.warn("Server socket is not limited to loopback connections");
     }
     this.listener = new ServerSocket(this.port, flags, 1);
     this.listener.asyncListen(this);