Problem with residuetypes.dat

GROMACS version: 2020.3
GROMACS modification: Yes

Good morning everyone.
I added a new residue to the amber99SB.ff force field following the guide present in the gromacs manual. When I use pdb2gmx it shows a fatal error saying that the novel residue has type “Other” although I added it to the residuetypes.dat file as type “Protein”. How can I solve this?

you can check that

  • pdb2gmx is reading the correct residuetypes.dat
  • the sintax of residuestypes.dat is correct
  • the new residue is well defined in all the aminoacid.* file of the modified amber force fields
    Best regards