Permission problem with create tablespace

I'm trying to create a new tablespace in a directory that postgres
owns, but PG says it cannot set permissions on this directory.

[root(at)localhost ~]# su - postgres
-bash-3.1$ mkdir /opt/home/pgdata/mspace/
-bash-3.1$ psql
Welcome to psql 8.1.4, the PostgreSQL interactive terminal.

Type: \copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit

postgres=# CREATE TABLESPACE mspace LOCATION '/opt/home/pgdata/mspace';
ERROR: could not set permissions on directory
"/opt/home/pgdata/mspace": Permission denied
postgres=# \q
-bash-3.1$ chmod 700 /opt/home/pgdata/mspace/
-bash-3.1$ whoami
postgres
-bash-3.1$

This is on Fedora Core 5 (x86), psql 8.1.4.

Andras