ERROR: isInList: The parameter at index 1 must be of type enum

Hi,

I have this "Visisble if" formula. $service_product_c is a multi picklist field.
I want the field to be visible when the value "Business integration" is selected.

I tried:
equal("Business integration",$service_product_c) // This works, but no other values can be selected.
isInList("Business integration",$service_product_c)
isInList(enum("Business integration"),$service_product_c)

How do I get the enum the error is asking for?

Regards,
Stijn