# Fatal errors

**URL:** <https://gromacs.bioexcel.eu/t/fatal-errors/5895>\
**Category:** User discussions\
**Tags:** pdb2gmx\
**Created:** [March 1, 2023, 2:16pm UTC](https://gromacs.bioexcel.eu/t/fatal-errors/5895 "2023-03-01T14:16:29Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Rickyy\_maybe](https://avatars.discourse-cdn.com/v4/letter/r/b5a626/32.png) [@Rickyy\_maybe](https://gromacs.bioexcel.eu/u/Rickyy_maybe)\
**Post date:** [March 1, 2023, 2:16pm UTC](https://gromacs.bioexcel.eu/t/fatal-errors/5895/1 "2023-03-01T14:16:29Z")

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GROMACS version: 2020.1-Ubuntu-2020.1-1  
GROMACS modification: Yes/No  
Here post your question

Fatal error:  
The residues in the chain GLY1–UNK37 do not have a consistent type. The first  
residue has type ‘Protein’, while residue UNK18 is of type ‘Other’. Either  
there is a mistake in your chain, or it includes nonstandard residue names  
that have not yet been added to the residuetypes.dat file in the GROMACS  
library directory. If there are other molecules such as ligands, they should  
not have the same chain ID as the adjacent protein chain since it’s a separate  
molecule.

I`ve connected the CYS with Avogadro2 and I`m facing this problem. How can I sole it?