diff --git a/moment/moment.d.ts b/moment/moment.d.ts
index 344885f1b..ffd01a4f6 100644
--- a/moment/moment.d.ts
+++ b/moment/moment.d.ts
@@ -25,7 +25,7 @@ interface MomentInput {
 
 interface Duration {
 
-    humanize(): string;
+    humanize(withSuffix?: boolean): string;
 
     milliseconds(): number;
     asMilliseconds(): number;