diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index d28167ea2da..8c646fe074f 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -1549,7 +1549,7 @@ declare module 'vscode' {
 	export interface NotebookController {
 
 		/**
-		 * The unique identifier of this notebook controller.
+		 * The identifier of this notebook controller.
 		 */
 		readonly id: string;
 
@@ -1673,7 +1673,7 @@ declare module 'vscode' {
 		/**
 		 * Creates a new notebook controller.
 		 *
-		 * @param id Unique identifier of the controller
+		 * @param id Extension-unique identifier of the controller
 		 * @param selector A notebook selector to narrow down notebook type or path
 		 * @param label The label of the controller
 		 * @param handler
diff --git a/src/vs/workbench/api/common/extHostNotebookKernels.ts b/src/vs/workbench/api/common/extHostNotebookKernels.ts
index f511caa1b61..add0d63d666 100644
--- a/src/vs/workbench/api/common/extHostNotebookKernels.ts
+++ b/src/vs/workbench/api/common/extHostNotebookKernels.ts
@@ -39,7 +39,7 @@ export class ExtHostNotebookKernels implements ExtHostNotebookKernelsShape {
 	createNotebookController(extension: IExtensionDescription, id: string, viewType: string, label: string, handler?: vscode.NotebookExecuteHandler, preloads?: vscode.NotebookKernelPreload[]): vscode.NotebookController {
 
 		for (let data of this._kernelData.values()) {
-			if (data.controller.id === id) {
+			if (data.controller.id === id && ExtensionIdentifier.equals(extension.identifier, data.extensionId)) {
 				throw new Error(`notebook controller with id '${id}' ALREADY exist`);
 			}
 		}
@@ -56,7 +56,7 @@ export class ExtHostNotebookKernels implements ExtHostNotebookKernelsShape {
 		const onDidReceiveMessage = new Emitter<{ editor: vscode.NotebookEditor, message: any }>();
 
 		const data: INotebookKernelDto2 = {
-			id,
+			id: `${extension.identifier.value}/${id}`,
 			viewType,
 			extensionId: extension.identifier,
 			extensionLocation: extension.extensionLocation,
@@ -92,7 +92,7 @@ export class ExtHostNotebookKernels implements ExtHostNotebookKernelsShape {
 		};
 
 		const controller: vscode.NotebookController = {
-			get id() { return data.id; },
+			get id() { return id; },
 			get viewType() { return data.viewType; },
 			onDidChangeNotebookAssociation: onDidChangeSelection.event,
 			get label() {