Hi, I added a new transition to my statemachine that is built around boost::msm and I got this error when compiling. error: wrong number of template arguments (21, should be 20) /boost/mpl/aux_/sequence_wrapper.hpp:154: error: provided for 'template<class T0, class T1, class T2, class T3, class T4, class T5, class T6, class T7, class T8, class T9, class T10, class T11, class T12, class T13, class T14, class T15, class T16, class T17, class T18, class T19> struct boost::mpl::vector' I went to add in the beginning of the header file before any boost includes: #define BOOST_MPL_LIMIT_LIST_SIZE 30 But that didn't fix it. I also tried adding in the makefile.am AM_CFLAGS = \ -DBOOST_MPL_LIMIT_LIST_SIZE=30 \ But that didn't fix it either. And then I hacked boost/mpl/limits/list.hpp and I changed the default value of BOOST_MPL_LIMIT_LIST_SIZE from 20 to 30 and I still have this error. Any idea? Thanks, Kamel