diff --git a/components/lib/timeline/Timeline.d.ts b/components/lib/timeline/Timeline.d.ts
index 4b13a4d87..411d8fe3d 100644
--- a/components/lib/timeline/Timeline.d.ts
+++ b/components/lib/timeline/Timeline.d.ts
@@ -10,7 +10,16 @@ import { VNode } from 'vue';
 import { ComponentHooks } from '../basecomponent';
 import { ClassComponent, GlobalComponentConstructor } from '../ts-helpers';
 
-export declare type TimelinePassThroughOptionType = TimelinePassThroughAttributes | null | undefined;
+export declare type TimelinePassThroughOptionType = TimelinePassThroughAttributes | ((options: TimelinePassThroughMethodOptions) => TimelinePassThroughAttributes | string) | string | null | undefined;
+
+/**
+ * Custom passthrough(pt) option method.
+ */
+export interface TimelinePassThroughMethodOptions {
+    instance: any;
+    props: TimelineProps;
+    context: TimelineContext;
+}
 
 /**
  * Custom passthrough(pt) options.
@@ -59,6 +68,16 @@ export interface TimelinePassThroughAttributes {
     [key: string]: any;
 }
 
+/**
+ * Defines current options in Timeline component.
+ */
+export interface TimelineContext {
+    /**
+     * Current index of the item as a number.
+     */
+    index: number;
+}
+
 /**
  * Defines valid properties in Timeline component.
  */