pg_dump: WARNING: could not find operator

Hello! I'm in the process of migrating some 10.23 database instances to 15.3, and I'm getting these warnings when doing
apg_dumpall on one of the servers: 

pg_dump: WARNING: could not find operator with OID 2234078
pg_dump: WARNING: could not find operator with OID 2234199

Is this indicative of a problem that I should fix before running pg_upgrade? If so, how?

And how do I find out what these OIDs are and what's referencing them?

Thanks,
Ed