diff --git a/modules/mol/base/src/impl/chain_impl.hh b/modules/mol/base/src/impl/chain_impl.hh
index feb03df4e2ca827c930a92b4192141cf691b8d8e..a3a7a97dcec720f024c39a2bcf73ff0bc108e9b6 100644
--- a/modules/mol/base/src/impl/chain_impl.hh
+++ b/modules/mol/base/src/impl/chain_impl.hh
@@ -69,7 +69,8 @@ public:
   {
     return type_==CHAINTYPE_POLY || this->IsPolypeptide() || 
            this->IsPolynucleotide() || this->IsPolysaccharide() ||
-           type_==CHAINTYPE_POLY_PEPTIDE_DN_RN;
+           type_==CHAINTYPE_POLY_PEPTIDE_DN_RN ||
+           type_==CHAINTYPE_OLIGOSACCHARIDE;
   }
   /// \brief whether the chain is a polysaccharide
   bool IsPolysaccharide() const