Frozen atoms in NPT ensemble

GROMACS version: 2019.1
GROMACS modification: No

Dear all,
I want to run MD simulation for a protein in membrane, with a single residue frozen completely. For membrane simulations, I have to use semiisotropic NPT ensemble. However, NPT does not work with frozen groups. I have found that previously energy group exclusions could be applied, which are now not supported. How can this issue be solved?

Thank you in advance,
Dmitrii

You will need to use a version that supports the group scheme (which I thought 2019 did, but if not, roll back to 2018) or otherwise simply use very strong position restraints. Freezing is entirely unphysical, anyway.