--- a/testing/marionette/listener.js
+++ b/testing/marionette/listener.js
@@ -82,17 +82,16 @@ var syncChrome = proxy.toChrome(sendSync
 var cookies = new Cookies(() => curContainer.frame.document, syncChrome);
 
 Cu.import("resource://gre/modules/Log.jsm");
 var logger = Log.repository.getLogger("Marionette");
 // Append only once to avoid duplicated output after listener.js gets reloaded
 if (logger.ownAppenders.length == 0) {
   logger.addAppender(new Log.DumpAppender());
 }
-logger.debug("loaded listener.js");
 
 var modalHandler = function() {
   // This gets called on the system app only since it receives the mozbrowserprompt event
   sendSyncMessage("Marionette:switchedToFrame", {frameValue: null, storePrevious: true});
   let isLocal = sendSyncMessage("MarionetteFrame:handleModal", {})[0].value;
   if (isLocal) {
     previousContainer = curContainer;
   }
@@ -299,17 +298,17 @@ var loadListener = {
   observe: function (subject, topic, data) {
     const winID = subject.QueryInterface(Components.interfaces.nsISupportsPRUint64).data;
     const curWinID = curContainer.frame.QueryInterface(Ci.nsIInterfaceRequestor)
         .getInterface(Ci.nsIDOMWindowUtils).outerWindowID;
 
     logger.debug(`Received observer notification "${topic}" for "${winID}"`);
 
     switch (topic) {
-      // In the case when the currently selected frame is about to close,
+      // In the case when the currently selected frame is closed,
       // there will be no further load events. Stop listening immediately.
       case "outer-window-destroyed":
         if (curWinID === winID) {
           this.stop();
           sendOk(this.command_id);
         }
         break;
     }
@@ -385,16 +384,18 @@ var loadListener = {
 
 /**
  * Called when listener is first started up.
  * The listener sends its unique window ID and its current URI to the actor.
  * If the actor returns an ID, we start the listeners. Otherwise, nothing happens.
  */
 function registerSelf() {
   let msg = {value: winUtil.outerWindowID};
+  logger.debug(`Register listener.js for window ${msg.value}`);
+
   // register will have the ID and a boolean describing if this is the main process or not
   let register = sendSyncMessage("Marionette:register", msg);
 
   if (register[0]) {
     let {id, remotenessChange} = register[0][0];
     capabilities = session.Capabilities.fromJSON(register[0][1]);
     listenerId = id;
     if (typeof id != "undefined") {