diff --git a/changelogs/server_server/newsfragments/1100.clarification b/changelogs/server_server/newsfragments/1100.clarification
new file mode 100644
index 00000000..e17a2538
--- /dev/null
+++ b/changelogs/server_server/newsfragments/1100.clarification
@@ -0,0 +1 @@
+Clarify that state keys starting with `@` are in fact reserved. Regressed from [#3658](https://github.com/matrix-org/matrix-spec-proposals/pull/3658).
\ No newline at end of file
diff --git a/data/api/server-server/space_hierarchy.yaml b/data/api/server-server/space_hierarchy.yaml
index cb30fa0f..834848c9 100644
--- a/data/api/server-server/space_hierarchy.yaml
+++ b/data/api/server-server/space_hierarchy.yaml
@@ -158,7 +158,7 @@ paths:
                                   format: int64
                                   description: The `origin_server_ts` for the event.
                               required: [origin_server_ts]
-                    required: [room_type, allowed_room_ids, children_state]
+                    required: [children_state]
               children:
                 type: array
                 description: |-