Filter Based Outbound Synchronization Rule not provisioning new Groups

Hi everybody

I'm trying to setup an outbound synchronization rule to provision groups into active directory. I'm filtering for <customBooleanAttribute> equal "true". Create resource in external system is true and I have the following flows:

initial: CustomExpression -> dn
member->member
accountName->sAMAccountName
CustomExpression -> groupType

The sync rule is syncing already existing groups with new data, if I change membership for example. But newly created groups in the MIM Portal aren't projected into the AD mgmt agent.

Is there anything I might have forgotten about?