diff --git a/dbms/src/Storages/MergeTree/MergeTreeData.cpp b/dbms/src/Storages/MergeTree/MergeTreeData.cpp
index 6f6c43facf8..29aafc1aa45 100644
--- a/dbms/src/Storages/MergeTree/MergeTreeData.cpp
+++ b/dbms/src/Storages/MergeTree/MergeTreeData.cpp
@@ -1645,7 +1645,7 @@ void MergeTreeData::alterSettings(
         const Context & context,
         TableStructureWriteLockHolder & table_lock_holder)
 {
-    std::unique_lock lock(settings_mutex);
+    std::lock_guard lock(settings_mutex);
     MutableMergeTreeSettingsPtr settings = std::move(*guarded_settings.getPtr()).mutate();
     settings->updateFromChanges(new_changes);
     IStorage::alterSettings(new_changes, current_database_name, current_table_name, context, table_lock_holder);