diff --git a/src/public/app/entities/fattachment.ts b/src/public/app/entities/fattachment.ts
index 484b55705..3966a2e05 100644
--- a/src/public/app/entities/fattachment.ts
+++ b/src/public/app/entities/fattachment.ts
@@ -61,6 +61,10 @@ class FAttachment {
       return this.ownerId;
     }
 
+    getContentLength() {
+      return this.contentLength;
+    }
+
     getUtcDateScheduledForErasureSince() {
       return this.utcDateScheduledForErasureSince;
     }
diff --git a/src/public/app/widgets/attachment_detail.ts b/src/public/app/widgets/attachment_detail.ts
index 5b37a94c2..99ee002fe 100644
--- a/src/public/app/widgets/attachment_detail.ts
+++ b/src/public/app/widgets/attachment_detail.ts
@@ -164,7 +164,7 @@ export default class AttachmentDetailWidget extends BasicWidget {
             $deletionWarning.hide();
         }
 
-        this.$wrapper.find(".attachment-details").text(t("attachment_detail_2.role_and_size", { role: this.attachment.role, size: utils.formatSize(this.attachment.contentLength) }));
+        this.$wrapper.find(".attachment-details").text(t("attachment_detail_2.role_and_size", { role: this.attachment.role, size: utils.formatSize(this.attachment.getContentLength()) }));
         this.$wrapper.find(".attachment-actions-container").append(this.attachmentActionsWidget.render());
 
         const { $renderedContent } = await contentRenderer.getRenderedContent(this.attachment, { imageHasZoom: this.isFullDetail });