diff --git a/hive-c0re/src/matrix.rs b/hive-c0re/src/matrix.rs
index d76d6480..0205c1e4 100644
--- a/hive-c0re/src/matrix.rs
+++ b/hive-c0re/src/matrix.rs
@@ -1266,6 +1266,13 @@ pub async fn ensure_hive_chat_room(
         let body = serde_json::json!({
             "name": HIVE_CHAT_ROOM_NAME,
             "topic": HIVE_CHAT_ROOM_TOPIC,
+            // Pin the room version explicitly: the `restricted` join rule
+            // below needs room version >= 8. tuwunel's default is currently
+            // higher, but pinning makes the dependency explicit so a future
+            // homeserver-default change can't silently invalidate the
+            // restricted rule (which would quietly fall back to invite-only
+            // and break the "operator joins from the Space" path).
+            "room_version": "10",
             "preset": "private_chat",
             "visibility": "private",
             "initial_state": [