diff --git a/optimizer-fix-controls.md b/optimizer-fix-controls.md
index b75d1033235be..dbe7e9126885d 100644
--- a/optimizer-fix-controls.md
+++ b/optimizer-fix-controls.md
@@ -103,7 +103,7 @@ SET SESSION tidb_opt_fix_control = '44262:ON,44389:ON';
 
 ### [`52869`](https://github.com/pingcap/tidb/issues/52869) <span class="version-mark">New in v8.1.0</span>
 
-- Default value: `OFF`
+- Default value: `ON`. Before v8.5.7, the default value is `OFF`.
 - Possible values: `ON`, `OFF`
 - As stated in the **Note** of [Explain Statements Using Index Merge](/explain-index-merge.md#examples), if the optimizer can choose the single index scan method (other than full table scan) for a query plan, the optimizer will not automatically use index merge.
 - You can remove this limitation by enabling this fix control. Removing this limitation enables the optimizer to choose index merge automatically in more queries, but might cause the optimizer to ignore the optimal execution plans. Therefore, it is recommended to conduct sufficient tests on actual use cases before removing this limitation to make sure that it will not cause performance regressions.