address-events

1 files changed, 6 insertions, 2 deletions

diff --git a/src/mailman/core/docs/chains.rst b/src/mailman/core/docs/chains.rst
index e3190e364..48b8c8858 100644
--- a/src/mailman/core/docs/chains.rst
+++ b/src/mailman/core/docs/chains.rst
@@ -32,9 +32,13 @@ The `discard` chain simply throws the message away.
     ... An important message.
     ... """)
 
+    >>> from mailman.interfaces.chain import ChainEvent
+
     >>> def print_msgid(event):
-    ...     print('{0}: {1}'.format(
-    ...         event.chain.name.upper(), event.msg.get('message-id', 'n/a')))
+    ...     if isinstance(event, ChainEvent):
+    ...         print('{0}: {1}'.format(
+    ...             event.chain.name.upper(),
+    ...             event.msg.get('message-id', 'n/a')))
 
     >>> from mailman.core.chains import process
     >>> from mailman.testing.helpers import event_subscribers