diff --git a/dbms/src/DataStreams/ParallelParsingBlockInputStream.cpp b/dbms/src/DataStreams/ParallelParsingBlockInputStream.cpp
index b8b961b3717..cb5b730b540 100644
--- a/dbms/src/DataStreams/ParallelParsingBlockInputStream.cpp
+++ b/dbms/src/DataStreams/ParallelParsingBlockInputStream.cpp
@@ -81,10 +81,7 @@ void ParallelParsingBlockInputStream::parserThreadFunction(size_t current_unit_n
             auto block = readers[current_unit_number]->read();
 
             blocks[current_unit_number].block.push_back(block);
-            {
-                std::lock_guard missing_values_lock(missing_values_mutex);
-                blocks[current_unit_number].block_missing_values.push_back(readers[current_unit_number]->getMissingValues());
-            }
+            blocks[current_unit_number].block_missing_values.push_back(readers[current_unit_number]->getMissingValues());
 
             if (block == Block())
                 break;
diff --git a/dbms/src/DataStreams/ParallelParsingBlockInputStream.h b/dbms/src/DataStreams/ParallelParsingBlockInputStream.h
index 3f2801f63e5..37fa5f23136 100644
--- a/dbms/src/DataStreams/ParallelParsingBlockInputStream.h
+++ b/dbms/src/DataStreams/ParallelParsingBlockInputStream.h
@@ -106,7 +106,6 @@ protected:
 
     const BlockMissingValues & getMissingValues() const override
     {
-        std::lock_guard missing_values_lock(missing_values_mutex);
         return last_block_missing_values;
     }
 
@@ -118,7 +117,6 @@ private:
     std::atomic<bool> is_exception_occured{false};
 
     BlockMissingValues last_block_missing_values;
-    mutable std::mutex missing_values_mutex;
 
     // Original ReadBuffer to read from.
     ReadBuffer & original_buffer;