diff --git a/vscode.proposed.d.ts b/vscode.proposed.d.ts
index f05140f18c..38b8847fb7 100644
--- a/vscode.proposed.d.ts
+++ b/vscode.proposed.d.ts
@@ -239,6 +239,11 @@ declare module 'vscode' {
 		 * When false, insecure outputs like HTML, JavaScript, SVG will not be rendered.
 		 */
 		trusted?: boolean;
+
+		/**
+		 * Languages the document supports
+		 */
+		languages?: string[];
 	}
 
 	export interface NotebookDocumentContentOptions {