diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index 19c09b024ffaa70c8e335b298f6097a483b99a81..f9d4ec038b3443019de1fd3ffd569431a5d5e1d9 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -1760,11 +1760,12 @@ declare module 'vscode' {
 
 		export function registerNotebookOutputRenderer(type: string, outputSelector: NotebookOutputSelector, renderer: NotebookOutputRenderer): Disposable;
 
+		// remove activeNotebookDocument, now that there is activeNotebookEditor.document
 		export let activeNotebookDocument: NotebookDocument | undefined;
 
 		export let activeNotebookEditor: NotebookEditor | undefined;
 
-		// export const onDidChangeNotebookDocument: Event<NotebookDocumentChangeEvent>;
+		export const onDidChangeNotebookDocument: Event<NotebookDocumentChangeEvent>;
 
 		/**
 		 * Create a document that is the concatenation of all  notebook cells. By default all code-cells are included
diff --git a/src/vs/workbench/api/common/extHost.api.impl.ts b/src/vs/workbench/api/common/extHost.api.impl.ts
index 8c79b302bc64b57dab476193e6b7ccb6717a7b86..4b48dc255dd2d18f336efe821e6f78f2a0e4ce99 100644
--- a/src/vs/workbench/api/common/extHost.api.impl.ts
+++ b/src/vs/workbench/api/common/extHost.api.impl.ts
@@ -917,6 +917,10 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 				checkProposedApiEnabled(extension);
 				return extHostNotebook.activeNotebookEditor;
 			},
+			onDidChangeNotebookDocument(listener, thisArgs?, disposables?) {
+				checkProposedApiEnabled(extension);
+				return extHostNotebook.onDidChangeNotebookDocument(listener, thisArgs, disposables);
+			},
 			createConcatTextDocument(notebook, selector) {
 				checkProposedApiEnabled(extension);
 				return new ExtHostNotebookConcatDocument(extHostNotebook, extHostDocuments, notebook, selector);