diff --git a/event-schemas/schema/core-event-schema/sync_room_event.yaml b/event-schemas/schema/core-event-schema/sync_room_event.yaml
index fbbf154f..8006148f 100644
--- a/event-schemas/schema/core-event-schema/sync_room_event.yaml
+++ b/event-schemas/schema/core-event-schema/sync_room_event.yaml
@@ -31,7 +31,8 @@ properties:
   origin_server_ts:
     description: Timestamp in milliseconds on originating homeserver
       when this event was sent.
-    type: number
+    type: integer
+    format: int64
   unsigned:
     description: Contains optional extra information about the event.
     properties:
diff --git a/event-schemas/schema/core-event-schema/sync_state_event.yaml b/event-schemas/schema/core-event-schema/sync_state_event.yaml
index 30af9698..1b6ce9b2 100644
--- a/event-schemas/schema/core-event-schema/sync_state_event.yaml
+++ b/event-schemas/schema/core-event-schema/sync_state_event.yaml
@@ -28,6 +28,10 @@ properties:
     description: A unique key which defines the overwriting semantics for this piece
       of room state. This value is often a zero-length string. The presence of this
       key makes this event a State Event.
+
+      State keys starting with an ``@`` are reserved for referencing user IDs, such
+      as room members. With the exception of a few events, state events set with a
+      given user's ID as the state key MUST only be set by that user.
     type: string
 required:
 - state_key