diff --git a/modules/mmcif/pyext/src/data.py b/modules/mmcif/pyext/src/data.py
index 53b8fbfac0..688496fc8c 100644
--- a/modules/mmcif/pyext/src/data.py
+++ b/modules/mmcif/pyext/src/data.py
@@ -199,7 +199,9 @@ def add(self, chain, entity):
                 self._used_entities.add(entity)
                 # Assign entity name from the component; strip out anything
                 # after a @ or .
-                entity.description = component.name.split("@")[0].split(".")[0]
+                if component.name:
+                    entity.description = \
+                        component.name.split("@")[0].split(".")[0]
             self._all_components.append(component)
             if modeled:
                 asym = ihm.AsymUnit(entity, name, id=asym_id)
diff --git a/modules/mmcif/test/test_data.py b/modules/mmcif/test/test_data.py
index 2104e85c73..94764a85fe 100644
--- a/modules/mmcif/test/test_data.py
+++ b/modules/mmcif/test/test_data.py
@@ -98,13 +98,17 @@ def test_entity_naming(self):
         system = ihm.System()
         cm = IMP.mmcif.data._ComponentMapper(system)
         entity1 = ihm.Entity("ANC")
+        entity2 = ihm.Entity("AC")
         chain1 = MockChain("A.1@12")
         chain2 = MockChain("A.2@12")
+        chain3 = MockChain(None)
         comp1 = cm.add(chain1, entity1)
         comp2 = cm.add(chain2, entity1)
+        comp3 = cm.add(chain3, entity2)
         self.assertEqual(chain1.name, "A.1@12")
         self.assertEqual(chain2.name, "A.2@12")
-        self.assertEqual(entity1.description, 'A')
+        self.assertIsNone(chain3.name)
+        self.assertIsNone(entity2.description)
 
     def test_component_mapper_same_id_chain(self):
         """Test ComponentMapper given two chains with same ID"""