current segfault if autovauum is on

It seems I get a segfault in backend if autovacuum is enabled. Here is
the backtrace when I connect to backend by using psql:

Program received signal SIGSEGV, Segmentation fault.
0x081fe737 in AtEOXact_GUC (isCommit=1 '\001', isSubXact=0 '\0') at guc.c:3139
3139 if (stack->nest_level < my_level)
(gdb) bt
#0 0x081fe737 in AtEOXact_GUC (isCommit=1 '\001', isSubXact=0 '\0') at guc.c:3139
#1 0x08099599 in CommitTransaction () at xact.c:1575
#2 0x08099c85 in CommitTransactionCommand () at xact.c:2184
#3 0x081fb529 in InitPostgres (dbname=0x82fde08 "test", username=0x82ec760 "t-ishii") at postinit.c:537
#4 0x0818c9b3 in PostgresMain (argc=6, argv=0x82ec780, username=0x82ec760 "t-ishii") at postgres.c:2959
#5 0x0816ba7a in BackendRun (port=0x8300480) at postmaster.c:2917
#6 0x0816b42f in BackendStartup (port=0x8300480) at postmaster.c:2564
#7 0x081699d7 in ServerLoop () at postmaster.c:1277
#8 0x08168e71 in PostmasterMain (argc=3, argv=0x82eaf68) at postmaster.c:980
#9 0x08131f58 in main (argc=3, argv=0x82eaf68) at main.c:254
#10 0x40087c1f in __libc_start_main () from /lib/i686/libc.so.6

Any idea?
--
Tatsuo Ishii
SRA OSS, Inc. Japan