diff --git a/ckanext/harvest/logic/action/update.py b/ckanext/harvest/logic/action/update.py
index 62e4c08..ae6f431 100644
--- a/ckanext/harvest/logic/action/update.py
+++ b/ckanext/harvest/logic/action/update.py
@@ -140,14 +140,22 @@ def harvest_source_clear(context,data_dict):
         delete from resource_group where package_id  in 
         (select id from package where state = 'to_delete');
         '''
+    # CKAN pre-2.5: authz models were removed in migration 078
+    if toolkit.check_ckan_version(max_version='2.4'):
+        sql += '''
+        delete from user_object_role where id not in 
+        (select user_object_role_id from package_role) and context = 'Package';
+        delete from package_role where package_id in 
+        (select id from package where state = 'to_delete');
+        '''
+
+
     sql += '''
     delete from harvest_object_error where harvest_object_id in (select id from harvest_object where harvest_source_id = '{harvest_source_id}');
     delete from harvest_object_extra where harvest_object_id in (select id from harvest_object where harvest_source_id = '{harvest_source_id}');
     delete from harvest_object where harvest_source_id = '{harvest_source_id}';
     delete from harvest_gather_error where harvest_job_id in (select id from harvest_job where source_id = '{harvest_source_id}');
     delete from harvest_job where source_id = '{harvest_source_id}';
-    delete from package_role where package_id in (select id from package where state = 'to_delete' );
-    delete from user_object_role where id not in (select user_object_role_id from package_role) and context = 'Package';
     delete from package_tag_revision where package_id in (select id from package where state = 'to_delete');
     delete from member_revision where table_id in (select id from package where state = 'to_delete');
     delete from package_extra_revision where package_id in (select id from package where state = 'to_delete');