--- a/testing/web-platform/tests/domparsing/DOMParser-parseFromString-encoding.html
+++ b/testing/web-platform/tests/domparsing/DOMParser-parseFromString-encoding.html
@@ -9,17 +9,17 @@
 
 function assertEncoding(doc) {
   assert_equals(doc.charset, "UTF-8", "document.charset");
   assert_equals(doc.characterSet, "UTF-8", "document.characterSet");
   assert_equals(doc.inputEncoding, "UTF-8", "document.characterSet");
 }
 
 setup(() => {
-  assert_precondition(document.characterSet === "windows-1252", "the meta charset must be in effect, making the main document windows-1252");
+  assert_equals(document.characterSet, "windows-1252", "the meta charset must be in effect, making the main document windows-1252");
 });
 
 test(() => {
   const parser = new DOMParser();
   const doc = parser.parseFromString("", "text/html");
 
   assertEncoding(doc);
 }, "HTML: empty");