diff --git a/ext/xsl/tests/gh21496.phpt b/ext/xsl/tests/gh21496.phpt
index 7a5cea37937d..12ff202aed17 100644
--- a/ext/xsl/tests/gh21496.phpt
+++ b/ext/xsl/tests/gh21496.phpt
@@ -3,6 +3,7 @@ GH-21496 (UAF in dom_objects_free_storage when importing non-document node as st
 --EXTENSIONS--
 dom
 xsl
+simplexml
 --CREDITS--
 YuanchengJiang
 --FILE--