diff --git a/src/lib/es2020.intl.d.ts b/src/lib/es2020.intl.d.ts
index f0938eca850f9..16f1a46750f4e 100644
--- a/src/lib/es2020.intl.d.ts
+++ b/src/lib/es2020.intl.d.ts
@@ -277,6 +277,7 @@ declare namespace Intl {
     };
 
      interface DisplayNamesOptions {
+        locale: UnicodeBCP47LocaleIdentifier;
         localeMatcher: RelativeTimeFormatLocaleMatcher;
         style: RelativeTimeFormatStyle;
         type: "language" | "region" | "script" | "currency";