diff --git a/src/vs/workbench/contrib/notebook/test/testNotebookEditor.ts b/src/vs/workbench/contrib/notebook/test/testNotebookEditor.ts
index 819ace7e8639624b0412434d1e8c910003bc7c4b..88b63e02f91d9c481d23969176a3cc6eb9342b20 100644
--- a/src/vs/workbench/contrib/notebook/test/testNotebookEditor.ts
+++ b/src/vs/workbench/contrib/notebook/test/testNotebookEditor.ts
@@ -169,8 +169,9 @@ export class TestNotebookEditor implements INotebookEditor {
 		// throw new Error('Method not implemented.');
 		return;
 	}
-	layoutNotebookCell(cell: CellViewModel, height: number): void {
+	async layoutNotebookCell(cell: CellViewModel, height: number): Promise<void> {
 		// throw new Error('Method not implemented.');
+		return;
 	}
 	createInset(cell: CellViewModel, output: IOutput, shadowContent: string, offset: number): void {
 		// throw new Error('Method not implemented.');