diff --git a/CHANGELOG.md b/CHANGELOG.md
index 571be26..0c75842 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## 1.0.1 under development
 
 - Enh #146: Explicitly import `SORT_ASC` constant in `QueryDataReader` (@vjik)
+- Enh #147: Omit `ASC` in `ORDER BY` for sort fields mapped to expressions (@vjik)
 
 ## 1.0.0 December 13, 2025
 
diff --git a/src/QueryDataReader.php b/src/QueryDataReader.php
index fd23255..94fa751 100644
--- a/src/QueryDataReader.php
+++ b/src/QueryDataReader.php
@@ -345,10 +345,9 @@ private function convertSortToOrderBy(Sort $sort): array
             if (is_string($field)) {
                 $result[$field] = $direction;
             } else {
-                $result[] = new CompositeExpression([
-                    $field,
-                    $direction === SORT_ASC ? 'ASC' : 'DESC',
-                ]);
+                $result[] = $direction === SORT_ASC
+                    ? $field
+                    : new CompositeExpression([$field, 'DESC']);
             }
         }
         return $result;
diff --git a/tests/Sqlite/QueryDataReader/QueryDataReaderTest.php b/tests/Sqlite/QueryDataReader/QueryDataReaderTest.php
index 0b107a1..1dcea33 100644
--- a/tests/Sqlite/QueryDataReader/QueryDataReaderTest.php
+++ b/tests/Sqlite/QueryDataReader/QueryDataReaderTest.php
@@ -4,10 +4,12 @@
 
 namespace Yiisoft\Data\Db\Tests\Sqlite\QueryDataReader;
 
+use PHPUnit\Framework\Attributes\DataProvider;
 use Yiisoft\Data\Db\QueryDataReader;
 use Yiisoft\Data\Db\Tests\Base\BaseQueryDataReaderTestCase;
 use Yiisoft\Data\Db\Tests\Sqlite\DatabaseTrait;
 use Yiisoft\Data\Reader\Sort;
+use Yiisoft\Db\Expression\Expression;
 use Yiisoft\Db\Query\Query;
 use Yiisoft\Test\Support\Log\SimpleLogger;
 
@@ -105,4 +107,23 @@ public function testCountQuery(): void
             $messages[0]['message'],
         );
     }
+
+    public static function dataSortWithFieldMappedToExpression(): iterable
+    {
+        yield 'asc' => ['asc', 'LOWER(name)'];
+        yield 'desc' => ['desc', 'LOWER(name) DESC'];
+    }
+
+    #[DataProvider('dataSortWithFieldMappedToExpression')]
+    public function testSortWithFieldMappedToExpression(string $direction, string $expectedOrderBy): void
+    {
+        $query = (new Query($this->getConnection()))->from('customer');
+        $dataReader = (new QueryDataReader($query, fieldMapper: ['userName' => new Expression('LOWER(name)')]))
+            ->withSort(Sort::any()->withOrder(['userName' => $direction]));
+
+        $this->assertSame(
+            'SELECT * FROM "customer" ORDER BY ' . $expectedOrderBy,
+            $dataReader->getPreparedQuery()->createCommand()->getRawSql(),
+        );
+    }
 }