diff --git a/core/modules/rdf/tests/src/Functional/GetNamespacesTest.php b/core/modules/rdf/tests/src/Functional/GetNamespacesTest.php
index 4ced14d..abdecc2 100644
--- a/core/modules/rdf/tests/src/Functional/GetNamespacesTest.php
+++ b/core/modules/rdf/tests/src/Functional/GetNamespacesTest.php
@@ -26,22 +26,23 @@ public function testGetRdfNamespaces() {
     // Fetches the front page and extracts RDFa 1.1 prefixes.
     $this->drupalGet('');
 
-    $element = $this->xpath('//html[contains(@prefix, :prefix_binding)]', [
+    $element = $this->xpath('//*[ancestor::html[contains(@prefix, :prefix_binding)]]', [
       ':prefix_binding' => 'rdfs: http://www.w3.org/2000/01/rdf-schema#',
     ]);
+
     $this->assertTrue(!empty($element[0]->getText()), 'A prefix declared once is displayed.');
 
-    $element = $this->xpath('//html[contains(@prefix, :prefix_binding)]', [
+    $element = $this->xpath('//*[ancestor::html[contains(@prefix, :prefix_binding)]]', [
       ':prefix_binding' => 'foaf: http://xmlns.com/foaf/0.1/',
     ]);
     $this->assertTrue(!empty($element[0]->getText()), 'The same prefix declared in several implementations of hook_rdf_namespaces() is valid as long as all the namespaces are the same.');
 
-    $element = $this->xpath('//html[contains(@prefix, :prefix_binding)]', [
+    $element = $this->xpath('//*[ancestor::html[contains(@prefix, :prefix_binding)]]', [
       ':prefix_binding' => 'foaf1: http://xmlns.com/foaf/0.1/',
     ]);
     $this->assertTrue(!empty($element[0]->getText()), 'Two prefixes can be assigned the same namespace.');
 
-    $element = $this->xpath('//html[contains(@prefix, :prefix_binding)]', [
+    $element = $this->xpath('//*[ancestor::html[contains(@prefix, :prefix_binding)]]', [
       ':prefix_binding' => 'dc: http://purl.org/dc/terms/',
     ]);
     $this->assertTrue(!empty($element[0]->getText()), 'When a prefix has conflicting namespaces, the first declared one is used.');