diff --git a/modules/mol/alg/pymod/lddt.py b/modules/mol/alg/pymod/lddt.py
index 91419c91e5f40f2a9d5c1b53c3abcf9297986572..4f8565bc71df07c61fb24bf8e2194273b76c01ad 100644
--- a/modules/mol/alg/pymod/lddt.py
+++ b/modules/mol/alg/pymod/lddt.py
@@ -814,7 +814,7 @@ class lDDTScorer:
             # throw away compound_lib info
             if r.chem_class.IsPeptideLinking():
                 self.compound_anames[r.name] = ["CA"]
-            elif r.chem_type.IsNucleotideLinking():
+            elif r.chem_class.IsNucleotideLinking():
                 self.compound_anames[r.name] = ["C3'"]
             else:
                 raise RuntimeError(f"Only support amino acids and nucleotides "