diff --git a/src/vs/workbench/contrib/notebook/browser/notebookEditorInput.ts b/src/vs/workbench/contrib/notebook/browser/notebookEditorInput.ts
index 50747e94bde21f47ecdb59936a069bbf0d3a106e..7cfae93b735072fad2caadcd75464b08ea076eb0 100644
--- a/src/vs/workbench/contrib/notebook/browser/notebookEditorInput.ts
+++ b/src/vs/workbench/contrib/notebook/browser/notebookEditorInput.ts
@@ -218,7 +218,7 @@ export class NotebookEditorInput extends EditorInput {
 	}
 
 	async backup(): Promise<IWorkingCopyBackup> {
-		return {};
+		throw new Error();
 	}
 
 	matches(otherInput: unknown): boolean {