diff --git a/synapse/storage/schema/delta/46/user_dir_typos.sql b/synapse/storage/schema/delta/46/user_dir_typos.sql
index 83ac0f2cef..d9505f8da1 100644
--- a/synapse/storage/schema/delta/46/user_dir_typos.sql
+++ b/synapse/storage/schema/delta/46/user_dir_typos.sql
@@ -16,7 +16,9 @@
 -- this is just embarassing :|
 ALTER TABLE users_in_pubic_room RENAME TO users_in_public_rooms;
 
-DROP INDEX users_in_pubic_room_room_idx;
-DROP INDEX users_in_pubic_room_user_idx;
+-- this is only 300K rows on matrix.org and takes ~3s to generate the index,
+-- so is hopefully not going to block anyone else for that long...
 CREATE INDEX users_in_public_rooms_room_idx ON users_in_public_rooms(room_id);
 CREATE UNIQUE INDEX users_in_public_rooms_user_idx ON users_in_public_rooms(user_id);
+DROP INDEX users_in_pubic_room_room_idx;
+DROP INDEX users_in_pubic_room_user_idx;