mkvextract crashes with non-Matroska files as the source

Hi all, well, i was little curious and i found mkvmerge -i works with ssa files, so i think extract it with mkvextract, and there we can get this error:

mkvextract tracks a.ssa 0:aaa
(gdb) bt full
#0  0x00007ffff76ec4ca in libebml::EbmlMaster::FindFirstElt(libebml::EbmlCallbacks const&, bool) () from /usr/lib64/libebml.so.4
No symbol table info available.
#1  0x00005555556322bb in kax_analyzer_c::determine_webm() ()
No symbol table info available.
#2  0x0000555555635b57 in kax_analyzer_c::process_internal() ()
No symbol table info available.
#3  0x0000555555638ec0 in kax_analyzer_c::process() ()
No symbol table info available.
#4  0x000055555559cb01 in open_and_analyze(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, kax_analyzer_c::parse_mode_e, bool) ()
No symbol table info available.
#5  0x00005555555863c2 in main ()
No symbol table info available.

Cya.