Issue for BOOST_PP_REMOVE_PARENS macro

I'm now using BOOST preprocess library for generate set/get/to_json/from_json code automatically. But I find some problem when using BOOST_PP_REMOVE_PARENS macro. Please check it.
Follow is the code in remove_parens.hpp with line 24-36.
The code for line 31 which should be (param) not (param)() in the original code.

#define BOOST_PP_REMOVE_PARENS(param) \
BOOST_PP_IIF \
( \
BOOST_PP_IS_BEGIN_PARENS(param), \
BOOST_PP_REMOVE_PARENS_DO, \
BOOST_PP_IDENTITY \
) \
(param)() \ /// The content should be (param) not (param)().
/**/

#define BOOST_PP_REMOVE_PARENS_DO(param) \
BOOST_PP_IDENTITY(BOOST_PP_TUPLE_ENUM(param)) \
/**/