diff --git a/dbms/src/DataStreams/MergingAggregatedMemoryEfficientBlockInputStream.cpp b/dbms/src/DataStreams/MergingAggregatedMemoryEfficientBlockInputStream.cpp
index 608bc06b713..4cdc2655933 100644
--- a/dbms/src/DataStreams/MergingAggregatedMemoryEfficientBlockInputStream.cpp
+++ b/dbms/src/DataStreams/MergingAggregatedMemoryEfficientBlockInputStream.cpp
@@ -179,8 +179,9 @@ void MergingAggregatedMemoryEfficientBlockInputStream::start()
             auto thread_group = CurrentThread::getGroup();
             reading_pool->schedule([&child, thread_group]
             {
-                CurrentThread::attachToIfDetached(thread_group);
                 setThreadName("MergeAggReadThr");
+                if (thread_group)
+                    CurrentThread::attachToIfDetached(thread_group);
                 CurrentMetrics::Increment metric_increment{CurrentMetrics::QueryThread};
                 child->readPrefix();
             });
@@ -485,8 +486,9 @@ MergingAggregatedMemoryEfficientBlockInputStream::BlocksToMerge MergingAggregate
                 auto thread_group = CurrentThread::getGroup();
                 reading_pool->schedule([&input, &read_from_input, thread_group]
                 {
-                    CurrentThread::attachToIfDetached(thread_group);
                     setThreadName("MergeAggReadThr");
+                    if (thread_group)
+                        CurrentThread::attachToIfDetached(thread_group);
                     CurrentMetrics::Increment metric_increment{CurrentMetrics::QueryThread};
                     read_from_input(input);
                 });
diff --git a/dbms/src/DataStreams/PushingToViewsBlockOutputStream.cpp b/dbms/src/DataStreams/PushingToViewsBlockOutputStream.cpp
index 096a7b1fe2a..f54c62b3579 100644
--- a/dbms/src/DataStreams/PushingToViewsBlockOutputStream.cpp
+++ b/dbms/src/DataStreams/PushingToViewsBlockOutputStream.cpp
@@ -91,7 +91,8 @@ void PushingToViewsBlockOutputStream::write(const Block & block)
             pool.schedule([=]
             {
                 setThreadName("PushingToViewsBlockOutputStream");
-                CurrentThread::attachToIfDetached(thread_group);
+                if (thread_group)
+                    CurrentThread::attachToIfDetached(thread_group);
                 process(block, view_num);
             });
         }
diff --git a/dbms/src/Interpreters/Aggregator.cpp b/dbms/src/Interpreters/Aggregator.cpp
index 2019ad9f04e..bfa8d51c9c3 100644
--- a/dbms/src/Interpreters/Aggregator.cpp
+++ b/dbms/src/Interpreters/Aggregator.cpp
@@ -1352,7 +1352,8 @@ BlocksList Aggregator::prepareBlocksAndFillTwoLevelImpl(
 {
     auto converter = [&](size_t bucket, ThreadGroupStatusPtr thread_group)
     {
-        CurrentThread::attachToIfDetached(thread_group);
+        if (thread_group)
+            CurrentThread::attachToIfDetached(thread_group);
         return convertOneBucketToBlock(data_variants, method, final, bucket);
     };
 
@@ -1805,7 +1806,8 @@ private:
         try
         {
             setThreadName("MergingAggregtd");
-            CurrentThread::attachToIfDetached(thread_group);
+            if (thread_group)
+                CurrentThread::attachToIfDetached(thread_group);
             CurrentMetrics::Increment metric_increment{CurrentMetrics::QueryThread};
 
             /// TODO: add no_more_keys support maybe
@@ -2127,7 +2129,8 @@ void Aggregator::mergeStream(const BlockInputStreamPtr & stream, AggregatedDataV
 
         auto merge_bucket = [&bucket_to_blocks, &result, this](Int32 bucket, Arena * aggregates_pool, ThreadGroupStatusPtr thread_group)
         {
-            CurrentThread::attachToIfDetached(thread_group);
+            if (thread_group)
+                CurrentThread::attachToIfDetached(thread_group);
 
             for (Block & block : bucket_to_blocks[bucket])
             {
diff --git a/dbms/src/Storages/Distributed/DistributedBlockOutputStream.cpp b/dbms/src/Storages/Distributed/DistributedBlockOutputStream.cpp
index 39e78ffd363..2464d15e624 100644
--- a/dbms/src/Storages/Distributed/DistributedBlockOutputStream.cpp
+++ b/dbms/src/Storages/Distributed/DistributedBlockOutputStream.cpp
@@ -196,7 +196,8 @@ ThreadPool::Job DistributedBlockOutputStream::runWritingJob(DistributedBlockOutp
     auto thread_group = CurrentThread::getGroup();
     return [this, thread_group, &job, &current_block]()
     {
-        CurrentThread::attachToIfDetached(thread_group);
+        if (thread_group)
+            CurrentThread::attachToIfDetached(thread_group);
         setThreadName("DistrOutStrProc");
 
         ++job.blocks_started;