diff --git a/Classes/Form/Element/SelectMultipleSideBySideElement_old.php b/Classes/Form/Element/SelectMultipleSideBySideElement.php
index 2e0caf7b..3a9649ec 100644
--- a/Classes/Form/Element/SelectMultipleSideBySideElement_old.php
+++ b/Classes/Form/Element/SelectMultipleSideBySideElement.php
@@ -402,7 +402,11 @@ class SelectMultipleSideBySideElement extends AbstractFormElement
         $html[] = '</div>';
 
         $resultArray['javaScriptModules'][] = JavaScriptModuleInstruction::create(
-            '@typo3/backend/form-engine/element/select-multiple-side-by-side-element.js'
+            '@typo3/backend/form-engine/element/select-multiple-side-by-side-element.js',
+        )->instance($selectedOptionsFieldId, $availableOptionsFieldId);
+
+        $resultArray['javaScriptModules'][] = JavaScriptModuleInstruction::create(
+            '@nl/sitepackage/select-multiple-side-by-side-element-copyext.js',
         )->instance($selectedOptionsFieldId, $availableOptionsFieldId);
 
         $resultArray['html'] = implode(LF, $html);