diff -r 0b8022b3abae -r c2ad3e682684 src/protocols/msn/switchboard.c
--- a/src/protocols/msn/switchboard.c	Fri Dec 03 00:10:19 2004 +0000
+++ b/src/protocols/msn/switchboard.c	Fri Dec 03 00:57:21 2004 +0000
@@ -529,7 +529,8 @@
 
 	msg = cmd->trans->data;
 
-	msg->ack_cb(msg->ack_data);
+	if (msg->ack_cb != NULL)
+		msg->ack_cb(msg->ack_data);
 
 	msn_message_unref(msg);
 }