Why doesn't this assemble for elf but does for pe?

[Stephen P. Smith]

I have some code that looks like this.  The code assembles when compiled 
with  i686-pc-pe-as but
chokes when compiled with i686-pc-elf-as.  The version of the assembler 
is the same:

$ i686-pc-elf-as --version
GNU assembler 030415 20030415
Copyright 2002 Free Software Foundation, Inc.
This program is free software; you may redistribute it under the terms of
the GNU General Public License.  This program has absolutely no warranty.
This assembler was configured for a target of `i686-pc-elf'.

Does anyone have a clue?

--------------------- example ------------
  .equ numRawHandlers, NumEntries
table:
       <some code goes here>
common:
.equ size, ((common - table/ numRawHandlers)