Is expiation (kaffara) or making up for the fast (qada') obligatory upon someone who completed their fast after masturbating during the day in Ramadan?

If masturbation does not result in the emission of semen, then the fast is valid. However, if it does result in the emission of semen, then the fast is invalidated, and one must make up that day without a severe expiation (kaffarah mughalladhah).