diff --git a/ydb/library/yql/core/ut/yql_column_order_ut.cpp b/ydb/library/yql/core/ut/yql_column_order_ut.cpp
index 38e012b5dfda..9d5e1d07e23d 100644
--- a/ydb/library/yql/core/ut/yql_column_order_ut.cpp
+++ b/ydb/library/yql/core/ut/yql_column_order_ut.cpp
@@ -9,12 +9,6 @@ using namespace NYql;
 
 Y_UNIT_TEST_SUITE(TYqlColumnOrder) {
 
-    Y_UNIT_TEST(ColumnOrderIgnoreCase) {
-        TColumnOrder order;
-        UNIT_ASSERT_EQUAL(order.AddColumn("a"), "a");
-        UNIT_ASSERT_EQUAL(order.AddColumn("A"), "A_generated_2");
-    }
-
     Y_UNIT_TEST(ColumnOrderShrink) {
         TColumnOrder order;
         UNIT_ASSERT_EQUAL(order.AddColumn("a"), "a");
diff --git a/ydb/library/yql/core/yql_type_annotation.cpp b/ydb/library/yql/core/yql_type_annotation.cpp
index 92eed308c1b2..639c81443f2b 100644
--- a/ydb/library/yql/core/yql_type_annotation.cpp
+++ b/ydb/library/yql/core/yql_type_annotation.cpp
@@ -124,6 +124,7 @@ TString TColumnOrder::Find(const TString& name) const {
 TColumnOrder& TColumnOrder::operator=(const TColumnOrder& rhs) {
     GeneratedToOriginal_ = rhs.GeneratedToOriginal_;
     Order_ = rhs.Order_;
+    UseCountLcase_ = rhs.UseCountLcase_;
     UseCount_ = rhs.UseCount_;
     return *this;
 }
@@ -152,7 +153,7 @@ TString TColumnOrder::AddColumn(const TString& name) {
 
 bool TColumnOrder::IsDuplicatedIgnoreCase(const TString& name) const {
     auto it = UseCountLcase_.find(to_lower(name));
-    return it != UseCount_.end() && it->second > 1;
+    return it != UseCountLcase_.end() && it->second > 1;
 }
 
 void TColumnOrder::Shrink(size_t remain) {
@@ -179,6 +180,7 @@ void TColumnOrder::Clear() {
     Order_.clear();
     GeneratedToOriginal_.clear();
     UseCount_.clear();
+    UseCountLcase_.clear();
 }
 
 void TColumnOrder::EraseIf(const std::function<bool(const TString&)>& fn) {