diff --git a/src/BioHelpers_FABER/rmsd.py b/src/BioHelpers_FABER/rmsd.py
index cbfa95a8ee39d9aa55f3061faa84bd81dab20b51..b81568d0f99cef09775b51699b4cf7ae22e6ee88 100644
--- a/src/BioHelpers_FABER/rmsd.py
+++ b/src/BioHelpers_FABER/rmsd.py
@@ -163,7 +163,7 @@ def __get_chain_from_file(file: str) -> pdb.Chain.Chain:
         chain = next(structure.get_chains())
         return chain
     elif extension == ".cif":
-        structure = pdb.MMCifParser().get_structure("", file)[0]
+        structure = pdb.MMCIFParser().get_structure("", file)[0]
         chain = next(structure.get_chains())
         return chain
     else: