How can I use a custom field in Journey Conditions if it's present in Unified Profile?

I’m trying to implement suppression logic inside a Journey in AJO for cases where a user enters the journey before being flagged as suppressed.

I have a custom field group with a boolean field called isSuppressed, which I added to a profile-enabled schema. The ingestion works fine. I can see the field correctly populated in the Unified Profile.

The problem is: I need to use a Condition node to check isSuppressed == false before an email is sent. But when I try to configure the condition, the field does not appear in the list of available profile fields. I also tried using expression mode with profile.isSuppressed == false, but it returns a “field not found” error.

Using an audience is not a viable workaround because the profile might enter the journey before it’s suppressed, and audience reevaluation won’t remove them from the journey once they’re in.

Is there any way to expose this custom field so it can be used in journey conditions? Or does it need to be part of a specific schema or field group to be accessible?

Thanks in advance!