upgrade failure from 9.5 to head

My cross-version upgrade testing tool just threw up this failure, 
upgrading from 9.5 to head:
   CREATE ROLE "dummy_seclabel_user1";   CREATE ROLE   ALTER ROLE "dummy_seclabel_user1" WITH NOSUPERUSER INHERIT
CREATEROLENOCREATEDB LOGIN NOREPLICATION NOBYPASSRLS;   ALTER ROLE   SECURITY LABEL FOR "dummy" ON ROLE
"dummy_seclabel_user1"IS   'classified';   psql:pg_upgrade_dump_globals.sql:25: ERROR:  security label provider
"dummy"is not loaded
 


This error might not be terribly new - it's been masked by another 
earlier problem that I have now catered for in the tool.

cheers

andrew