diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index 68f9669759c2f4cad69696252a49f4e19cbe9594..48f4965829c37c686792ff52b48a17e377ab2e52 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -1827,7 +1827,7 @@ declare module 'vscode' {
 	}
 
 	export interface NotebookKernel {
-		readonly id: string;
+		readonly id?: string;
 		label: string;
 		description?: string;
 		isPreferred?: boolean;