diff --git a/vscode.proposed.d.ts b/vscode.proposed.d.ts
index 7b14a50952..a447086312 100644
--- a/vscode.proposed.d.ts
+++ b/vscode.proposed.d.ts
@@ -385,6 +385,11 @@ declare module 'vscode' {
 		readonly language: string;
 	}
 
+	export interface NotebookCellMetadataChangeEvent {
+		readonly document: NotebookDocument;
+		readonly cell: NotebookCell;
+	}
+
 	export interface NotebookCellData {
 		readonly cellKind: CellKind;
 		readonly source: string;
@@ -575,6 +580,7 @@ declare module 'vscode' {
 		export const onDidChangeNotebookCells: Event<NotebookCellsChangeEvent>;
 		export const onDidChangeCellOutputs: Event<NotebookCellOutputsChangeEvent>;
 		export const onDidChangeCellLanguage: Event<NotebookCellLanguageChangeEvent>;
+		export const onDidChangeCellMetadata: Event<NotebookCellMetadataChangeEvent>;
 		/**
 		 * Create a document that is the concatenation of all  notebook cells. By default all code-cells are included
 		 * but a selector can be provided to narrow to down the set of cells.