Fix #1491
diff --git a/libcloud/compute/drivers/openstack.py b/libcloud/compute/drivers/openstack.py
index 9362542..9130dc5 100644
--- a/libcloud/compute/drivers/openstack.py
+++ b/libcloud/compute/drivers/openstack.py
@@ -2841,6 +2841,8 @@
         self._ex_force_base_url = original_ex_force_base_url
         if original_ex_force_base_url:
             kwargs['ex_force_base_url'] = self._ex_force_base_url
+        elif 'ex_force_base_url' in kwargs:
+            del kwargs['ex_force_base_url']
         self.connectionCls = original_connectionCls
         super(OpenStack_2_NodeDriver, self).__init__(*args, **kwargs)