typo (#41044)

diff --git a/css/css-nesting/parsing.html b/css/css-nesting/parsing.html
index a533d86..b189190 100644
--- a/css/css-nesting/parsing.html
+++ b/css/css-nesting/parsing.html
@@ -27,7 +27,7 @@
     }, ruleText);
   }
 
-  function testInvalidSelector(sel {parent=".foo"}={}) {
+  function testInvalidSelector(sel, {parent=".foo"}={}) {
     resetStylesheet();
     const ruleText = `${parent} { ${sel} { color: green; }}`
     test(()=>{