diff --git a/modules/mol/alg/pymod/chain_mapping.py b/modules/mol/alg/pymod/chain_mapping.py
index 41f7f69755b56ecc04c36f494c6e469176032223..0fa35ad24e5f77417b76b090236137cf7882c0cd 100644
--- a/modules/mol/alg/pymod/chain_mapping.py
+++ b/modules/mol/alg/pymod/chain_mapping.py
@@ -3435,7 +3435,7 @@ def _ChainMappings(ref_chains, mdl_chains, n_max=None):
     iterators = list()
     for ref, mdl in zip(ref_chains, mdl_chains):
         if len(ref) == 0:
-            raise RuntimeError("Expext at least one chain in ref chem group")
+            raise RuntimeError("Expect at least one chain in ref chem group")
         if len(ref) == len(mdl):
             iterators.append(_RefEqualGenerator(ref, mdl))
         elif len(ref) < len(mdl):