diff --git a/typescript/widget/yearmonth/popup.yearmonth.ts b/typescript/widget/yearmonth/popup.yearmonth.ts
index 5f2400a6f..319a8d24a 100644
--- a/typescript/widget/yearmonth/popup.yearmonth.ts
+++ b/typescript/widget/yearmonth/popup.yearmonth.ts
@@ -7,7 +7,7 @@ export declare class DynamicYearMonthPopup extends Widget {
     static BUTTON_OK_EVENT_CHANGE: string;
     static EVENT_CHANGE: string;
 
-    setMinDate(minDate: string): void;
+    setMinDate(minDate?: string): void;
 
-    setMaxDate(maxDate: string): void;
+    setMaxDate(maxDate?: string): void;
 }