Deadlock in vacuum (check fails)

I found following strange error on gothic moth:


================== pgsql.22658/src/test/regress/regression.diffs 
===================
*** 
/zfs_data/home/postgres/buildfarm/gothic_moth/HEAD/pgsql.22658/src/test/regress/expected/vacuum.out 
Tue Jan 12 22:06:13 2010
--- 
/zfs_data/home/postgres/buildfarm/gothic_moth/HEAD/pgsql.22658/src/test/regress/results/vacuum.out 
Tue Jan 12 22:35:25 2010
***************
*** 94,99 ****
--- 94,103 ----  -- only non-system tables should be changed  VACUUM FULL pg_am;  VACUUM FULL pg_class;
+ ERROR:  deadlock detected
+ DETAIL:  Process 5913 waits for AccessExclusiveLock on relation 2662 
of database 16384; blocked by process 5915.
+ Process 5915 waits for AccessShareLock on relation 1259 of database 
16384; blocked by process 5913.
+ HINT:  See server log for query details.  VACUUM FULL pg_database;  VACUUM FULL vaccluster;  VACUUM FULL vacid;


Detail here:

http://www.pgbuildfarm.org/cgi-bin/show_log.pl?nm=gothic_moth&dt=2010-01-12%2021:06:01
Zdenek