--- a/quantum/db/db_base_plugin_v2.py
+++ b/quantum/db/db_base_plugin_v2.py
@@ -949,6 +949,13 @@ class QuantumDbPluginV2(quantum_plugin_base_v2.QuantumPluginBaseV2):

     def delete_network(self, context, id):
         with context.session.begin(subtransactions=True):
+            # clean up subnets
+            subnets_qry = context.session.query(models_v2.Subnet)
+            subnets =  subnets_qry.filter_by(network_id=id)
+            for subnet in subnets:
+                self.delete_subnet(context, subnet['id'])
+            subnets.delete()
+
             network = self._get_network(context, id)

             filter = {'network_id': [id]}
@@ -965,9 +972,6 @@ class QuantumDbPluginV2(quantum_plugin_base_v2.QuantumPluginBaseV2):
             for port in ports:
                 self._delete_port(context, port['id'])

-            # clean up subnets
-            subnets_qry = context.session.query(models_v2.Subnet)
-            subnets_qry.filter_by(network_id=id).delete()
             context.session.delete(network)

     def get_network(self, context, id, fields=None):