I reported it to upstream but it seems it doesn't get much attention https://gitlab.com/gromacs/gromacs/-/issues/3568 The patch is not too complicated... maybe we could include it (I can co-maintain if you want to get it updated when needed :/) --- src/gromacs/gmxana/gmx_do_dssp.cpp.old 2020-06-22 15:55:09.869741935 +0200 +++ src/gromacs/gmxana/gmx_do_dssp.cpp 2020-06-22 15:56:09.398482876 +0200 @@ -289,6 +289,10 @@ { *atoms->atomname[i] = OOO; } + else if (std::strcmp(*(atoms->atomname[i]), "OT1") == 0) + { + *atoms->atomname[i] = OOO; + } } } Thanks a lot