--- a/testing/marionette/server.js
+++ b/testing/marionette/server.js
@@ -319,16 +319,18 @@ server.TCPListener = class {
           this.alteredPrefs.add(k);
         }
       }
     }
 
     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);
 
     this.alive = true;
     this._acceptConnections = true;
   }