diff --git a/types/moment-timezone/index.d.ts b/types/moment-timezone/index.d.ts
index ca62b3cb82..c3927415c6 100644
--- a/types/moment-timezone/index.d.ts
+++ b/types/moment-timezone/index.d.ts
@@ -1,6 +1,6 @@
 // Type definitions for moment-timezone.js 0.5
 // Project: http://momentjs.com/timezone/
-// Definitions by: Michel Salib <https://github.com/michelsalib>
+// Definitions by: Michel Salib <https://github.com/michelsalib>, Alan Brazil Lins <https://github.com/alanblins>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
 import * as moment from 'moment';
@@ -51,7 +51,7 @@ declare module "moment" {
         }): void;
 
         names(): string[];
-        guess(): string;
+        guess(ignoreCache?: boolean): string;
 
         setDefault(timezone: string): void;
     }
diff --git a/types/moment-timezone/moment-timezone-tests.ts b/types/moment-timezone/moment-timezone-tests.ts
index 14df62915b..66bb7403ea 100644
--- a/types/moment-timezone/moment-timezone-tests.ts
+++ b/types/moment-timezone/moment-timezone-tests.ts
@@ -78,6 +78,8 @@ moment.tz.setDefault('America/Los_Angeles');
 
 moment.tz.guess();
 
+moment.tz.guess(true);
+
 const zoneAbbr: string = moment.tz('America/Los_Angeles').zoneAbbr();
 
 const zoneName: string = moment.tz('America/Los_Angeles').zoneName();