RDS PostgreSQL Read Replica extension not working: libpsl.so.5: cannot open shared object file

I have an RDS PostgreSQL db which I just upgraded to 16.4. It uses the PostGIS extension. It's working fine after the upgrade;

SELECT extname, extversion from pg_extension;
SELECT PostGIS_Version();

Tell me that the latest supported PostGIS (3.4.2) is installed, and the PostGIS_Version() function returns the correct info. When I try the same thing on the database's read replica, I see that the extensions are in the installed list, but...the PostGIS_Version() function gives this error:

ERROR: could not load library "/rdsdbbin/postgres-16.4.R1/lib/postgis-3.so": libpsl.so.5: cannot open shared object file: No such file or directory

Does this mean the instance is misconfigured? What can I do to help with this?