diff --git a/modules/mol/base/pymod/export_residue.cc b/modules/mol/base/pymod/export_residue.cc
index 60566cfa51ee08035ba25e13549038470bef5eb2..d0915dcd719b02502ba2158cac951fb91acea277 100644
--- a/modules/mol/base/pymod/export_residue.cc
+++ b/modules/mol/base/pymod/export_residue.cc
@@ -68,6 +68,7 @@ void export_Residue()
   class_<ChemClass>("ChemClass", init<char>(args("chem_class")))
     .def(self!=self)
     .def(self==self)
+    .def(self_ns::str(self))
     .def("IsPeptideLinking", &ChemClass::IsPeptideLinking)
     .def("IsNucleotideLinking", &ChemClass::IsNucleotideLinking)
   ;