chmod 0755 behaves like chmod 755

[Jason Pepas]

I think I might have found a bug regarding the new behavior of chmod 
(regarding the preservation of setuig, setgid, etc) in coreutils-6.9.

My understanding is that the new behavior should preserve these bits if 
they are not explicitly specified, and this appears to work correctly:

$ mkdir foo
$ ls -ld foo
drwxr-xr-x 2 cell dept 4096 Oct  2 13:46 foo
$ chmod g+s foo
$ ls -ld foo
drwxr-sr-x 2 cell dept 4096 Oct  2 13:46 foo
$ chmod 755 foo
$ ls -ld foo
drwxr-sr-x 2 cell dept 4096 Oct  2 13:46 foo

However, the problem exists for the case where a user *does* explicitly 
specify what those bits should be.  chmod respects those bits while 
setting them:

$ mkdir foo
$ ls -ld foo
drwxr-xr-x 2 cell dept 4096 Oct  2 13:40 foo
$ chmod 2755 foo
$ ls -ld foo
drwxr-sr-x 2 cell dept 4096 Oct  2 13:40 foo

but ignores them when the user attempts to clear them:

$ chmod 0755 foo
$ ls -ld foo
drwxr-sr-x 2 cell dept 4096 Oct  2 13:40 foo

However, using the symbolic instead of octal notation works correctly:

$ chmod g-s foo
$ ls -ld foo
drwxr-xr-x 2 cell dept 4096 Oct  2 13:40 foo

Is there any way to clear the setgid bit using octal notation?

-jason