diff --git a/roles/custom/matrix-synapse/defaults/main.yml b/roles/custom/matrix-synapse/defaults/main.yml
index 9a99d5cd1..214e1841c 100644
--- a/roles/custom/matrix-synapse/defaults/main.yml
+++ b/roles/custom/matrix-synapse/defaults/main.yml
@@ -416,8 +416,8 @@ matrix_synapse_root_log_level: "WARNING"
 
 # Rate limits
 matrix_synapse_rc_message:
-  per_second: 0.2
-  burst_count: 10
+  per_second: 0.5
+  burst_count: 30
 
 matrix_synapse_rc_registration:
   per_second: 0.17
@@ -1261,6 +1261,28 @@ matrix_synapse_experimental_features_msc4108_enabled: false
 # Set this to false if you still want to disable to API for some reason. Note that doing so breaks Element X compatibility though.
 matrix_synapse_experimental_features_msc3266_enabled: true
 
+# Controls whether to enable the "Delayed Events" experimental feature.
+# Delayed events are required for proper call (Element Call) participation signalling.
+# If disabled it is very likely that you end up with stuck calls in Matrix rooms.
+#
+# Related to `matrix_synapse_max_event_delay_duration`
+#
+# See https://github.com/matrix-org/matrix-spec-proposals/pull/4140
+matrix_synapse_experimental_features_msc4140_enabled: false
+
+# Controls the maximum allowed duration by which sent events can be delayed, as per MSC4140.
+#
+# See `matrix_synapse_experimental_features_msc4140_enabled`.
+matrix_synapse_max_event_delay_duration: 24h
+
+# Controls whether to enable the MSC4222 experimental feature (adding `state_after` to sync v2).
+#
+# Allow clients to opt-in to a change of the sync v2 API that allows them to correctly track the state of the room.
+# This is required by Element Call to track room state reliably.
+#
+# See https://github.com/matrix-org/matrix-spec-proposals/pull/4222
+matrix_synapse_experimental_features_msc4222_enabled: false
+
 # Enable this to activate the REST auth password provider module.
 # See: https://github.com/ma1uta/matrix-synapse-rest-password-provider
 matrix_synapse_ext_password_provider_rest_auth_enabled: false
diff --git a/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2 b/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2
index dbfbdffaf..9675bb245 100644
--- a/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2
+++ b/roles/custom/matrix-synapse/templates/synapse/homeserver.yaml.j2
@@ -2970,6 +2970,9 @@ background_updates:
     #default_batch_size: 50
 
 experimental_features:
+  {% if matrix_synapse_experimental_features_msc3266_enabled %}
+  msc3266_enabled: true
+  {% endif %}
   {% if matrix_synapse_experimental_features_msc3861_enabled %}
   msc3861:
     enabled: true
@@ -2984,8 +2987,15 @@ experimental_features:
   {% if matrix_synapse_experimental_features_msc4108_enabled %}
   msc4108_enabled: true
   {% endif %}
-  {% if matrix_synapse_experimental_features_msc3266_enabled %}
-  msc3266_enabled: true
+  {% if matrix_synapse_experimental_features_msc4140_enabled %}
+  msc4140_enabled: true
+  {% endif %}
+  {% if matrix_synapse_experimental_features_msc4222_enabled %}
+  msc4222_enabled: true
   {% endif %}
 
+{% if matrix_synapse_experimental_features_msc4140_enabled %}
+max_event_delay_duration: {{ matrix_synapse_max_event_delay_duration | to_json }}
+{% endif %}
+
 # vim:ft=yaml