diff --git a/changelog.d/19633.misc b/changelog.d/19633.misc
new file mode 100644
index 0000000000..37efd5309f
--- /dev/null
+++ b/changelog.d/19633.misc
@@ -0,0 +1 @@
+Document context for why increase timeout for policy server requests.
diff --git a/synapse/handlers/room_policy.py b/synapse/handlers/room_policy.py
index fee3c6cfaf..01943e1991 100644
--- a/synapse/handlers/room_policy.py
+++ b/synapse/handlers/room_policy.py
@@ -223,11 +223,16 @@ class RoomPolicyHandler:
             return
 
         # Ask the policy server to sign this event.
-        # We set a smallish timeout here as we don't want to block event sending too long.
         try:
             signature = await self._federation_client.ask_policy_server_to_sign_event(
                 policy_server.server_name,
                 event,
+                # We set a smallish timeout here as we don't want to block event sending
+                # too long.
+                #
+                # We were previously seeing regular timeouts with media
+                # scanning/checking when the timeout was set to 3s. 30s was chosen based
+                # on vibes and light real world testing.
                 timeout=30000,
             )
             # TODO: We can *probably* remove this when we remove unstable MSC4284 support.