Hi, Using an empty Index crashes. Should I really have to check if there is some text in a StringSet before building the index or is it a bug? This code: #include <seqan/index.h> int main( int argc, char * argv[] ) { using namespace seqan; typedef StringSet< String< Dna5 > > string_set_t; typedef Index< string_set_t > index_t; string_set_t seqs; index_t index( seqs ); Iterator< index_t, TopDown<> >::Type iterator( index ); return 0; } gives the following for a debug build: .... core/include/seqan/sequence/string_base.h:461 Assertion failed : static_cast<TStringPos>(pos) < static_cast<TStringPos>(length(me)) was: 0 >= 0 (Trying to access an element behind the last one!) Aborted (core dumped) I'm using svn version 14052 Regards, John.