diff --git a/oslo_db/sqlalchemy/models.py b/oslo_db/sqlalchemy/models.py
index 4293c9d..0c4e0de 100644
--- a/oslo_db/sqlalchemy/models.py
+++ b/oslo_db/sqlalchemy/models.py
@@ -54,7 +54,15 @@ class ModelBase(six.Iterator):
         return getattr(self, key)
 
     def __contains__(self, key):
-        return hasattr(self, key)
+        # Don't use hasattr() because hasattr() catches any exception, not only
+        # AttributeError. We want to passthrough SQLAlchemy exceptions
+        # (ex: sqlalchemy.orm.exc.DetachedInstanceError).
+        try:
+            getattr(self, key)
+        except AttributeError:
+            return False
+        else:
+            return True
 
     def get(self, key, default=None):
         return getattr(self, key, default)
diff --git a/oslo_db/tests/sqlalchemy/test_models.py b/oslo_db/tests/sqlalchemy/test_models.py
index 525573a..279c5c3 100644
--- a/oslo_db/tests/sqlalchemy/test_models.py
+++ b/oslo_db/tests/sqlalchemy/test_models.py
@@ -70,6 +70,18 @@ class ModelBaseTest(test_base.DbTestCase):
 
         self.assertFalse('non-existent-key' in mb)
 
+    def test_modelbase_contains_exc(self):
+        class ErrorModel(models.ModelBase):
+            @property
+            def bug(self):
+                raise ValueError
+
+        model = ErrorModel()
+        model.update({'attr': 5})
+
+        self.assertTrue('attr' in model)
+        self.assertRaises(ValueError, lambda: 'bug' in model)
+
     def test_modelbase_items_iteritems(self):
         h = {'a': '1', 'b': '2'}
         expected = {