diff --git a/src/IO/WriteBufferFromS3.cpp b/src/IO/WriteBufferFromS3.cpp
index 6207ba53bd8..2510b86716c 100644
--- a/src/IO/WriteBufferFromS3.cpp
+++ b/src/IO/WriteBufferFromS3.cpp
@@ -431,7 +431,7 @@ void WriteBufferFromS3::waitForReadyBackGroundTasks()
 {
     if (schedule)
     {
-        std::lock_guard lock(bg_tasks_mutex);
+        std::unique_lock lock(bg_tasks_mutex);
         {
             while (!upload_object_tasks.empty() && upload_object_tasks.front().is_finised)
             {
@@ -442,7 +442,7 @@ void WriteBufferFromS3::waitForReadyBackGroundTasks()
 
                 if (exception)
                 {
-                    waitForAllBackGroundTasks();
+                    waitForAllBackGroundTasksUnlocked(lock);
                     std::rethrow_exception(exception);
                 }
 
@@ -457,7 +457,15 @@ void WriteBufferFromS3::waitForAllBackGroundTasks()
     if (schedule)
     {
         std::unique_lock lock(bg_tasks_mutex);
-        bg_tasks_condvar.wait(lock, [this]() { return num_added_bg_tasks == num_finished_bg_tasks; });
+        waitForAllBackGroundTasksUnlocked(lock);
+    }
+}
+
+void WriteBufferFromS3::waitForAllBackGroundTasksUnlocked(std::unique_lock<std::mutex> & bg_tasks_lock)
+{
+    if (schedule)
+    {
+        bg_tasks_condvar.wait(bg_tasks_lock, [this]() { return num_added_bg_tasks == num_finished_bg_tasks; });
 
         while (!upload_object_tasks.empty())
         {
@@ -472,7 +480,7 @@ void WriteBufferFromS3::waitForAllBackGroundTasks()
 
         if (put_object_task)
         {
-            bg_tasks_condvar.wait(lock, [this]() { return put_object_task->is_finised; });
+            bg_tasks_condvar.wait(bg_tasks_lock, [this]() { return put_object_task->is_finised; });
             if (put_object_task->exception)
                 std::rethrow_exception(put_object_task->exception);
         }
diff --git a/src/IO/WriteBufferFromS3.h b/src/IO/WriteBufferFromS3.h
index 99440654910..712044841d0 100644
--- a/src/IO/WriteBufferFromS3.h
+++ b/src/IO/WriteBufferFromS3.h
@@ -84,6 +84,7 @@ private:
 
     void waitForReadyBackGroundTasks();
     void waitForAllBackGroundTasks();
+    void waitForAllBackGroundTasksUnlocked(std::unique_lock<std::mutex> & bg_tasks_lock);
 
     String bucket;
     String key;