Mass action, show products without price (free)

How can I show all products without price? I choose "price_value" but what should i choose in the next field? If i choose "0" or "IS NULL", all my 2599 products show up.
If I choose price_value=50, it work correct and shows me my products valued to 50.

Hi,

You are right, there is a problem with this kind of search.
I created an issue ticket, we will investigate on the error and make a patch. Xavier, who made the biggest part of the mass action system is not here this week, he will take a look when he will come back.

Regards,

Hi,

This correction will be in the next release