diff --git a/src/Storages/MergeTree/IMergeTreeDataPart.cpp b/src/Storages/MergeTree/IMergeTreeDataPart.cpp
index d4d3844de6c..45e5d9d92de 100644
--- a/src/Storages/MergeTree/IMergeTreeDataPart.cpp
+++ b/src/Storages/MergeTree/IMergeTreeDataPart.cpp
@@ -448,7 +448,12 @@ void IMergeTreeDataPart::setColumns(const NamesAndTypesList & new_columns)
     for (const auto & column : columns)
         column_name_to_position.emplace(column.name, pos++);
 
-    columns_description = ColumnsDescription(columns);
+    /// For wide parts convert plain arrays to Nested for
+    /// more convinient managing of shared offsets column.
+    if (part_type == Type::Wide)
+        columns_description = ColumnsDescription(Nested::collect(columns));
+    else
+        columns_description = ColumnsDescription(columns);
 }
 
 NameAndTypePair IMergeTreeDataPart::getColumn(const String & column_name) const
diff --git a/src/Storages/MergeTree/IMergeTreeReader.cpp b/src/Storages/MergeTree/IMergeTreeReader.cpp
index 2ae087deffa..a5ef2fa6ac8 100644
--- a/src/Storages/MergeTree/IMergeTreeReader.cpp
+++ b/src/Storages/MergeTree/IMergeTreeReader.cpp
@@ -42,12 +42,6 @@ IMergeTreeReader::IMergeTreeReader(
     , all_mark_ranges(all_mark_ranges_)
     , alter_conversions(storage.getAlterConversionsForPart(data_part))
 {
-    if (isWidePart(data_part))
-    {
-        /// For wide parts convert plain arrays of Nested to subcolumns
-        /// to allow to use shared offset column from cache.
-        columns = Nested::convertToSubcolumns(columns);
-    }
 }
 
 IMergeTreeReader::~IMergeTreeReader() = default;
diff --git a/src/Storages/MergeTree/MergeTreeDataPartWide.cpp b/src/Storages/MergeTree/MergeTreeDataPartWide.cpp
index 7fe68420310..3e5576b6bdf 100644
--- a/src/Storages/MergeTree/MergeTreeDataPartWide.cpp
+++ b/src/Storages/MergeTree/MergeTreeDataPartWide.cpp
@@ -49,7 +49,8 @@ IMergeTreeDataPart::MergeTreeReaderPtr MergeTreeDataPartWide::getReader(
 {
     auto ptr = std::static_pointer_cast<const MergeTreeDataPartWide>(shared_from_this());
     return std::make_unique<MergeTreeReaderWide>(
-        ptr, columns_to_read, metadata_snapshot, uncompressed_cache,
+        ptr, Nested::convertToSubcolumns(columns_to_read),
+        metadata_snapshot, uncompressed_cache,
         mark_cache, mark_ranges, reader_settings,
         avg_value_size_hints, profile_callback);
 }
@@ -64,7 +65,8 @@ IMergeTreeDataPart::MergeTreeWriterPtr MergeTreeDataPartWide::getWriter(
     const MergeTreeIndexGranularity & computed_index_granularity) const
 {
     return std::make_unique<MergeTreeDataPartWriterWide>(
-        shared_from_this(), data_part_storage_builder, columns_list, metadata_snapshot, indices_to_recalc,
+        shared_from_this(), data_part_storage_builder,
+        Nested::convertToSubcolumns(columns_list), metadata_snapshot, indices_to_recalc,
         index_granularity_info.marks_file_extension,
         default_codec_, writer_settings, computed_index_granularity);
 }