Table Maintenance Dialog - cannot update ?

Hi,

I've created a Z table called ZTEST with display/maintenance allowed

Generated maintenance dialog via SE11 -> Utilities -> Table Maintenance Generator

Authorization Group: &NC&

Authorization Object: S_TABU_DIS

Maintenance type: One Step

Overview screen: 1

Recording routine: Standard recording routine

Recording routine: or user, recording routine

(tried both recording routine settings)

Then went to SM30 -> ZTEST -> Maintain

Now, I am able to ADD or DELETE entries, but I am unable to MODIFY existing entries (Edit -> Change Field Contents gives me the following error: 'Table ZTEST has no relevant fields')

How can I fix that ?