diff --git a/src/Dto/Search/Query/Sort/CustomField.php b/src/Dto/Search/Query/Sort/CustomField.php
new file mode 100644
index 0000000..7fcb072
--- /dev/null
+++ b/src/Dto/Search/Query/Sort/CustomField.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Atoolo\Search\Dto\Search\Query\Sort;
+
+/**
+ * @codeCoverageIgnore
+ */
+class CustomField extends Criteria
+{
+    public function __construct(
+        public readonly string $field,
+        Direction $direction = Direction::ASC
+    ) {
+        parent::__construct($direction);
+    }
+}
diff --git a/src/Service/Search/Schema2xFieldMapper.php b/src/Service/Search/Schema2xFieldMapper.php
index 5071394..f7900f8 100644
--- a/src/Service/Search/Schema2xFieldMapper.php
+++ b/src/Service/Search/Schema2xFieldMapper.php
@@ -22,6 +22,7 @@
 use Atoolo\Search\Dto\Search\Query\Filter\RelativeDateRangeFilter;
 use Atoolo\Search\Dto\Search\Query\Filter\SiteFilter;
 use Atoolo\Search\Dto\Search\Query\Sort\Criteria;
+use Atoolo\Search\Dto\Search\Query\Sort\CustomField;
 use Atoolo\Search\Dto\Search\Query\Sort\Date;
 use Atoolo\Search\Dto\Search\Query\Sort\Headline;
 use Atoolo\Search\Dto\Search\Query\Sort\Name;
@@ -92,6 +93,8 @@ public function getSortField(Criteria $criteria): string
                 return 'sp_sortvalue';
             case $criteria instanceof Score:
                 return 'score';
+            case $criteria instanceof CustomField:
+                return $criteria->field;
             default:
                 throw new InvalidArgumentException(
                     'Unsupported sort criteria: ' . get_class($criteria)
diff --git a/test/Service/Search/Schema2xFieldMapperTest.php b/test/Service/Search/Schema2xFieldMapperTest.php
index 7c8404d..c7615f5 100644
--- a/test/Service/Search/Schema2xFieldMapperTest.php
+++ b/test/Service/Search/Schema2xFieldMapperTest.php
@@ -22,6 +22,7 @@
 use Atoolo\Search\Dto\Search\Query\Filter\RelativeDateRangeFilter;
 use Atoolo\Search\Dto\Search\Query\Filter\SiteFilter;
 use Atoolo\Search\Dto\Search\Query\Sort\Criteria;
+use Atoolo\Search\Dto\Search\Query\Sort\CustomField;
 use Atoolo\Search\Dto\Search\Query\Sort\Date;
 use Atoolo\Search\Dto\Search\Query\Sort\Headline;
 use Atoolo\Search\Dto\Search\Query\Sort\Name;
@@ -158,6 +159,15 @@ public function testGetSortField(
         );
     }
 
+    public function testGetSortCustomField(): void
+    {
+        $criteria = new CustomField('custom_field');
+        $this->assertEquals(
+            'custom_field',
+            $this->mapper->getSortField($criteria)
+        );
+    }
+
     public function testUnsupportedSortField(): void
     {
         $this->expectException(InvalidArgumentException::class);