diff --git a/moment/moment.d.ts b/moment/moment.d.ts
index 20e921c32..0ec575fd8 100644
--- a/moment/moment.d.ts
+++ b/moment/moment.d.ts
@@ -28,7 +28,7 @@ interface MomentInput {
 
 interface Duration {
 
-    humanize(): string;
+    humanize(withSuffix?: boolean): string;
 
     milliseconds(): number;
     asMilliseconds(): number;