GSettings are not saved

[Lanoxx <lanoxx gmx net>]

I have a very weired issue with GSettings in my application:

I am using the following code:

    g_settings_set_boolean (mainapp->settings, key, is_active);
    if(g_settings_get_has_unapplied (mainapp->settings)) {
        g_warning("Found unapplied settings");
    }

The warning is never printed, so I assume that the changes are applied 
directly, but when I restart my application, then all settings are 
forgotten. Is GSettings not supposed to remember the option through a 
restart of the application? Or ist there any other magic involved that I 
do not know about?

Kind Regards
Lanoxx