diff --git a/entity.py b/entity.py
index 713c248..fccce1b 100644
--- a/entity.py
+++ b/entity.py
@@ -493,10 +493,11 @@ def direct_instances(Class, world = None):
   def get_class_properties(Class):
     l = set()
     for r in _property_value_restrictions(Class, None):
-      if   r.property._class_property_some and ((r.type == VALUE) or (r.type == SOME) or ((r.type == EXACTLY) and r.cardinality >= 1) or ((r.type == MIN) and r.cardinality >= 1)):
-        l.add(r.property)
-      elif r.property._class_property_only and  (r.type == ONLY):
-        l.add(r.property)
+      prop = r.property
+      if   getattr(prop, "_class_property_some", False) and ((r.type == VALUE) or (r.type == SOME) or ((r.type == EXACTLY) and r.cardinality >= 1) or ((r.type == MIN) and r.cardinality >= 1)):
+        l.add(prop)
+      elif getattr(prop, "_class_property_only", False) and  (r.type == ONLY):
+        l.add(prop)
         
     for storid in Class.namespace.world._get_triples_s_p(Class.storid):
       Prop = Class.namespace.world._get_by_storid(storid)
@@ -507,10 +508,11 @@ def get_class_properties(Class):
   def INDIRECT_get_class_properties(Class):
     l = set()
     for r in _inherited_properties_value_restrictions(Class, None, set()):
-      if   r.property._class_property_some and ((r.type == VALUE) or (r.type == SOME) or ((r.type == EXACTLY) and r.cardinality >= 1) or ((r.type == MIN) and r.cardinality >= 1)):
-        l.add(r.property)
-      elif r.property._class_property_only and  (r.type == ONLY):
-        l.add(r.property)
+      prop = r.property
+      if   getattr(prop, "_class_property_some", False) and ((r.type == VALUE) or (r.type == SOME) or ((r.type == EXACTLY) and r.cardinality >= 1) or ((r.type == MIN) and r.cardinality >= 1)):
+        l.add(prop)
+      elif getattr(prop, "_class_property_only", False) and  (r.type == ONLY):
+        l.add(prop)
         
     for storid in Class.namespace.world._get_triples_s_p(Class.storid):
       Prop = Class.namespace.world._get_by_storid(storid)
diff --git a/test/regtest.py b/test/regtest.py
index 74c0301..8c038ae 100644
--- a/test/regtest.py
+++ b/test/regtest.py
@@ -5955,6 +5955,21 @@ class D(Thing):
     assert isinstance(r.property, Inverse)
     self.assert_triple(r.property.storid, owl_inverse_property, P.storid, None,  world)
     
+  def test_inverse_2_get_class_properties(self):
+    world = self.new_world()
+    n = world.get_ontology("http://www.test.org/test.owl")
+    
+    with n:
+      class P(ObjectProperty): pass
+      class C(Thing): pass
+      class D(Thing):
+        is_a = [Inverse(P).some(C)]
+      class E(D): pass
+      
+    assert set(D.get_class_properties()) == set()
+    assert set(D.INDIRECT_get_class_properties()) == set()
+    assert set(E.INDIRECT_get_class_properties()) == set()
+    
   def test_inverse_3(self):
     world = self.new_world()
     n = world.get_ontology("http://www.test.org/test.owl")