diff --git a/be/src/vec/core/block.h b/be/src/vec/core/block.h
index 94dd5ec8e9fd0e..ff8927c6823c33 100644
--- a/be/src/vec/core/block.h
+++ b/be/src/vec/core/block.h
@@ -121,7 +121,7 @@ class Block {
         raw_res_ptr->reserve(batch_size);
 
         // adapt for outer join change column to nullable
-        if (raw_res_ptr->is_nullable()) {
+        if (raw_res_ptr->is_nullable() && !input_col_ptr->is_nullable()) {
             auto col_ptr_nullable =
                     reinterpret_cast<vectorized::ColumnNullable*>(raw_res_ptr.get());
             col_ptr_nullable->get_null_map_column().insert_many_defaults(select_size);