part time flexi sick leave question

[sparkly72]

I work 14 hrs a week over 2 set days. Once a month I work on a Saturday- this takes me over my hours so I usually take the following mon off as TOIL. I have fairly flexible working so don't HAVE to take the mon off - I could save up the hours or take time off another time - my boss is pretty good.
If I am sick on the Saturday should I then work the Monday or does it still count as TOIL?
If it helps the Saturdays are rostered according to a work event that happens on a Saturday.