diff --git a/docs/parlor/design.txt b/docs/parlor/design.txt
index ee5c6f77c..0797b57c6 100644
--- a/docs/parlor/design.txt
+++ b/docs/parlor/design.txt
@@ -122,3 +122,6 @@ accepting and delivering an invitation.
 How to prune stale invitations since invitations are not set up to be tied
 to a location (in which case we could use occupant added/removed to
 trigger invite cleanup)?
+
+Add MessageHandler validators so that turn based games can easily reject
+message events from non-turn-holders.