SOLUTION
Recompile the RMAN packages and procedures by connecting to the target database as SYSDBA and execute:
$ sqlplus / as sysdba
SQL> @$ORACLE_HOME/rdbms/admin/dbmsrman.sql
SQL> @$ORACLE_HOME/rdbms/admin/dbmsbkrs.sql
SQL> @$ORACLE_HOME/rdbms/admin/prvtrmns.plb
SQL> @$ORACLE_HOME/rdbms/admin/prvtbkrs.plb