diff --git a/src/lib/es2017.intl.d.ts b/src/lib/es2017.intl.d.ts
index 2f9efc15fbbae..8c0f3cbf7ceb4 100644
--- a/src/lib/es2017.intl.d.ts
+++ b/src/lib/es2017.intl.d.ts
@@ -12,6 +12,7 @@ declare namespace Intl {
         timeZoneName: any
         weekday: any
         year: any
+        unknown: any
     }
 
     type DateTimeFormatPartTypes = keyof DateTimeFormatPartTypesRegistry;