diff --git a/hosts/nachtigall/apps/matrix/synapse.nix b/hosts/nachtigall/apps/matrix/synapse.nix
index 9a16c368..3dd71eef 100644
--- a/hosts/nachtigall/apps/matrix/synapse.nix
+++ b/hosts/nachtigall/apps/matrix/synapse.nix
@@ -188,6 +188,7 @@ in
         per_second = 0.17;
       };
       redaction_retention_period = "7d";
+      forgotten_room_retention_period = "7d";
       redis.enabled = false;
       registration_requires_token = false;
       registrations_require_3pid = [ "email" ];