PostGIS install not completing

Running psql (13.1, server 12.4) trying to install PostGIS.
OS X 10.13.6.
postgis installed via brew install postgis.

CREATE EXTENSION postgis;
ERROR:  could not load library "/usr/local/lib/postgresql/plpgsql.so": dlopen(/usr/local/lib/postgresql/plpgsql.so, 10): Symbol not found: _CachedPlanAllowsSimpleValidityCheck
  Referenced from: /usr/local/lib/postgresql/plpgsql.so
  Expected in: /usr/local/opt/postgresql/bin/postgres
 in /usr/local/lib/postgresql/plpgsql.so

While the source code referenced can be found for this symbol, I have no idea what is going on.
How to rectify it?