ahum.. tree construction question

here is my rule:
===========
compare : (shift -> shift)
(
( (LT | GT | LTE | GTE) s=shift -> ^((LT | GT | LTE | GTE) $compare
$s) )*
| is='is' i=identifier -> ^(IS[$is] $compare $i)
| as='as' i=identifier -> ^(AS[$as] $compare $i)
)
;
===========

it doesn't work...
it looks like think ANTLR doesn't like my ^((LT | GT | LTE | GTE) in the
tree rewriting rule.
any tip on how I could rewrite this tree?