JPQL query with multiple parameter to be used in a WHERE ... IN clause

Hi,
I'm stuck with the following : I want a JPQL custom query on my business object like this one :
SELECT m
FROM Mission m
WHERE m.poleGestion IN (:polesGestion)
ORDER BY m.dateEtape DESC

I can't tell bonita that the parameter polesGestion is a list of strings, and it doesn't work either if I provide the following string for the parameter polesGestion : "'Val1','Val2'".

Is there a solution to use the IN clause with a parameter in Bonita ?

Best regards,
Marina