diff --git a/lib/browser/guest-window-manager.js b/lib/browser/guest-window-manager.js
index 77777ae211db..e06dd27d203d 100644
--- a/lib/browser/guest-window-manager.js
+++ b/lib/browser/guest-window-manager.js
@@ -247,6 +247,8 @@ ipcMain.on('ELECTRON_GUEST_WINDOW_MANAGER_INTERNAL_WINDOW_OPEN', function (event
   if ((event.sender.isGuest() && !event.sender.allowPopups) || event.defaultPrevented) {
     if (newGuest !== undefined && newGuest !== null) {
       if (options.webContents === newGuest.webContents) {
+        // the webContents is not changed, so set defaultPrevented to false to
+        // stop the callers of this event from destroying the webContents.
         event.defaultPrevented = false
       }
       event.returnValue = setupGuest(event.sender, frameName, newGuest, options)