I cannot save custom temperaments

1) I make adjustments to a temperament.
2) I click save, choose a file name and save but no file is saved.
3) I click apply and the following dialog box appears:

Dialog:
Do you want to quit the plugin? (OK / Show details... / Cancel)
Detail box:
It looks like you have made customisations to this tuning, you could save them to a file before quitting if you like.