diff --git a/src/dom/document-cloner.ts b/src/dom/document-cloner.ts
index 08faa298d..e96d486af 100644
--- a/src/dom/document-cloner.ts
+++ b/src/dom/document-cloner.ts
@@ -27,7 +27,7 @@ import {DebuggerType, isDebugging} from '../core/debugger';
 
 export interface CloneOptions {
     ignoreElements?: (element: Element) => boolean;
-    onclone?: (document: Document, element: HTMLElement) => void;
+    onclone?: (document: Document, element: HTMLElement) => void | Promise<void>;
     allowTaint?: boolean;
 }