QComboBox with validator - handle focus out

Good morning,

I have an editable QComboBox with a QRegExpValidator. The validation itself works fine, but the ComboBox can remain in an invalid/intermediate state when it loses focus (the validation is performed on focus out, but the text does not change). What's the best way to deal with this situation?
My approach would be to save the old value and listen to the FocusOut-event. The I do the validation and if the result is not acceptable, i restore the old value.

Is there a better solution?

greetings,
Felix