diff --git a/dav_events/workflow.py b/dav_events/workflow.py
index c173c41..f1c012b 100644
--- a/dav_events/workflow.py
+++ b/dav_events/workflow.py
@@ -268,14 +268,16 @@ class BasicWorkflow(object):
         if heaviest_flag:
             last_status = heaviest_flag.status
             if last_status.code.startswith('publishing_'):
-                flags = event.flags.filter(status__code='accepted')
-                flags.append(heaviest_flag)
+                flags = []
+                flags += event.flags.filter(status__code='accepted')
+                flags += heaviest_flag
             elif last_status.code.startswith('published_'):
+                flags = []
                 if event.flags.filter(status__code='publishing').exists():
-                    flags = event.flags.filter(status__code='publishing')
+                    flags += event.flags.filter(status__code='publishing')
                 else:
-                    flags = event.flags.filter(status__code='accepted')
-                flags.append(heaviest_flag)
+                    flags += event.flags.filter(status__code='accepted')
+                flags += heaviest_flag
             elif last_status.code.startswith('clear'):
                 flags = [heaviest_flag]
                 flags += event.flags.filter(status__code__in=('canceled', 'realized'))