diff --git a/types/vis/index.d.ts b/types/vis/index.d.ts
index e4f8fe0dfd..1167c6db6a 100644
--- a/types/vis/index.d.ts
+++ b/types/vis/index.d.ts
@@ -180,7 +180,7 @@ interface TimelineOptions {
   onRemoveGroup?(): void; // TODO
   order?(): void; // TODO
   orientation?: TimelineOptionsOrientationType;
-  rollingMode: boolean;
+  rollingMode?: boolean;
   selectable?: boolean;
   showCurrentTime?: boolean;
   showMajorLabels?: boolean;