Search builder IN operator on a custom field

I have a custom field which is a mutiple checklist with options.
I just created a search builder based on this field
E.g.
Person -> Custom Field -> In -> Option 2 (OVL)

But this does not show all the contacts and on the result page it shows a query like RLIKE OVL (OVL is the value of the option).
If I change the query builder to the operator Rexexp the value is set to OVL and all the contacts are found.
So it looks like the operator IN does not work correctly on a multiple checkbox custom field.

Solution should be that the IN operator gets converted to another sql operator, such as a regular expression.