Postmaster fatal defect - pl/pgsql return type conversion

Using the head branch, when I execute the following in psql on Redhat 6.2
i386, the postmaster process dies gives an error message about corrupted
shared memory:

--begin---
create function bug1(integer) returns numeric as '
begin return $1;
end;'
language 'plpgsql';


select bug1(5);

---end---

Any ideas?
 - Mark Butler