diff --git a/src/Columns/ColumnNullable.cpp b/src/Columns/ColumnNullable.cpp
index 99d377f10eb..139323f9770 100644
--- a/src/Columns/ColumnNullable.cpp
+++ b/src/Columns/ColumnNullable.cpp
@@ -786,16 +786,17 @@ ColumnPtr ColumnNullable::getNestedColumnWithDefaultOnNull() const
     auto res = nested_column->cloneEmpty();
     const auto & null_map_data = getNullMapData();
     size_t start = 0;
+    size_t end = null_map->size();
     while (start < nested_column->size())
     {
         size_t next_null_index = start;
-        while (next_null_index < null_map->size() && !null_map_data[next_null_index])
+        while (next_null_index < end && !null_map_data[next_null_index])
             ++next_null_index;
 
         if (next_null_index != start)
             res->insertRangeFrom(*nested_column, start, next_null_index - start);
 
-        if (next_null_index < null_map->size())
+        if (next_null_index < end)
             res->insertDefault();
 
         start = next_null_index + 1;