diff --git a/src/dom/css-escape.ts b/src/dom/css-escape.ts
index 392ab3a82..064d117b3 100644
--- a/src/dom/css-escape.ts
+++ b/src/dom/css-escape.ts
@@ -33,4 +33,4 @@ function cssEscapePolyfill(ident: string): string {
   return result
 }
 
-export const cssEscape = CSS?.escape ?? cssEscapePolyfill
+export const cssEscape = window.CSS?.escape ?? cssEscapePolyfill