Sublime Text 3 don't see settings files from the .sublime-package

I've tried to use the new method of packaging as described in the porting guide — http://www.sublimetext.com/docs/3/porting_guide.html — but I use sublime.load_settings() in my plugin, and the file with settings is going with the plugin, so it's in the package.

But when I do so, the settings are not loaded — when I do sublime.load_settings("filename.json").get("settingname") it returns nothing when the plugin is packaged and returns the setting properly if it is not.