diff --git a/types/options.d.ts b/types/options.d.ts
index fb1c9cf1c..0d6ae8f36 100644
--- a/types/options.d.ts
+++ b/types/options.d.ts
@@ -42,7 +42,7 @@ export interface CoreAnnotationOptions extends AnnotationEvents, ShadowOptions,
   borderWidth?: Scriptable<number, PartialEventContext>,
   display?: Scriptable<boolean, PartialEventContext>,
   drawTime?: Scriptable<DrawTime, PartialEventContext>,
-  init: boolean | ((chart: Chart, properties: AnnotationBoxModel, options: AnnotationOptions) => void | boolean | AnnotationBoxModel),
+  init?: boolean | ((chart: Chart, properties: AnnotationBoxModel, options: AnnotationOptions) => void | boolean | AnnotationBoxModel),
   id?: string,
   xMax?: Scriptable<ScaleValue, PartialEventContext>,
   xMin?: Scriptable<ScaleValue, PartialEventContext>,