diff --git a/data-template/synapse/homeserver.yaml b/data-template/synapse/homeserver.yaml
index 3044a5f..f73f424 100644
--- a/data-template/synapse/homeserver.yaml
+++ b/data-template/synapse/homeserver.yaml
@@ -115,6 +115,10 @@ experimental_features:
   # MSC3266: Room summary API. Used for knocking over federation
   msc3266_enabled: true
 
+  # state_after in /sync v2, needed for reliable state in busy rooms
+  # especially Element Call
+  msc4222_enabled: true
+
 # The maximum allowed duration by which sent events can be delayed, as
 # per MSC4140. Must be a positive value if set.  Defaults to no
 # duration (null), which disallows sending delayed events.