toISOString function also return null

diff --git a/moment.d.ts b/moment.d.ts
index 2c5b3cf46bb437818e4143e15ca5007aec2b736d..85bbfe0492eb693d2e98f8e55eb55274d624c778 100644 (file)
--- a/moment.d.ts
+++ b/moment.d.ts
@@ -587,7 +587,7 @@ declare namespace moment {
 
     toArray(): number[];
     toDate(): Date;
-    toISOString(keepOffset?: boolean): string;
+    toISOString(keepOffset?: boolean): string | null;
     inspect(): string;
     toJSON(): string;
     unix(): number;