diff --git a/src/public/app/widgets/attachment_detail.js b/src/public/app/widgets/attachment_detail.ts
similarity index 96%
rename from src/public/app/widgets/attachment_detail.js
rename to src/public/app/widgets/attachment_detail.ts
index 8aa6b5824..819d7a2f1 100644
--- a/src/public/app/widgets/attachment_detail.js
+++ b/src/public/app/widgets/attachment_detail.ts
@@ -7,6 +7,7 @@ import imageService from "../services/image.js";
 import linkService from "../services/link.js";
 import contentRenderer from "../services/content_renderer.js";
 import toastService from "../services/toast.js";
+import type FAttachment from "../entities/fattachment.js";
 
 const TPL = `
 <div class="attachment-detail-widget">
@@ -96,7 +97,12 @@ const TPL = `
 </div>`;
 
 export default class AttachmentDetailWidget extends BasicWidget {
-    constructor(attachment, isFullDetail) {
+    attachment: FAttachment;
+    attachmentActionsWidget: AttachmentActionsWidget;
+    isFullDetail: boolean;
+    $wrapper!: JQuery<HTMLElement>;
+
+    constructor(attachment: FAttachment, isFullDetail: boolean) {
         super();
 
         this.contentSized();