diff --git a/types/moment-range/index.d.ts b/types/moment-range/index.d.ts
index 18538e5c6d..a7d2fd25e6 100644
--- a/types/moment-range/index.d.ts
+++ b/types/moment-range/index.d.ts
@@ -57,6 +57,7 @@ export class DateRange {
 export interface MomentRangeMethods {
     range(range: string | Date[] | moment.Moment[]): DateRange;
     range(start: Date | moment.Moment, end: Date | moment.Moment): DateRange;
+    isRange(range: any): range is DateRange;
     within(range: DateRange): boolean;
 }