diff --git a/src/vs/workbench/api/electron-browser/mainThreadComments.ts b/src/vs/workbench/api/electron-browser/mainThreadComments.ts
index 4b21dfb20271945da3512b82225d2f707f6cd684..369ec18bbfb48200f809735e7038565ff1636459 100644
--- a/src/vs/workbench/api/electron-browser/mainThreadComments.ts
+++ b/src/vs/workbench/api/electron-browser/mainThreadComments.ts
@@ -451,6 +451,13 @@ export class MainThreadComments extends Disposable implements MainThreadComments
 		this._commentService.setWorkspaceComments(String(handle), []);
 	}
 
+	$unregisterCommentController(handle: number): void {
+		const providerId = this._handlers.get(handle);
+		this._commentService.unregisterCommentController(providerId);
+		this._handlers.delete(handle);
+		this._commentControllers.delete(handle);
+	}
+
 	$updateCommentControllerFeatures(handle: number, features: CommentProviderFeatures): void {
 		let provider = this._commentControllers.get(handle);
 
diff --git a/src/vs/workbench/api/node/extHost.protocol.ts b/src/vs/workbench/api/node/extHost.protocol.ts
index cc56e4a101b76d9ebc7edb18af29743f5a052494..2ba6a6edd939c5102e8c7182e1d1a8f4fa6c91fd 100644
--- a/src/vs/workbench/api/node/extHost.protocol.ts
+++ b/src/vs/workbench/api/node/extHost.protocol.ts
@@ -121,6 +121,7 @@ export interface CommentProviderFeatures {
 
 export interface MainThreadCommentsShape extends IDisposable {
 	$registerCommentController(handle: number, id: string, label: string): void;
+	$unregisterCommentController(handle: number): void;
 	$updateCommentControllerFeatures(handle: number, features: CommentProviderFeatures): void;
 	$createCommentThread(handle: number, commentThreadHandle: number, threadId: string, resource: UriComponents, range: IRange, comments: modes.Comment[], acceptInputCommand: modes.Command | undefined, additionalCommands: modes.Command[], collapseState: modes.CommentThreadCollapsibleState): modes.CommentThread2 | undefined;
 	$deleteCommentThread(handle: number, commentThreadHandle: number): void;
diff --git a/src/vs/workbench/api/node/extHostComments.ts b/src/vs/workbench/api/node/extHostComments.ts
index 9f400a165b8ee1b425cade9c4424ca9b1f35997d..6d4247bdea3aa9c696ae337f35eae7ffaa9439de 100644
--- a/src/vs/workbench/api/node/extHostComments.ts
+++ b/src/vs/workbench/api/node/extHostComments.ts
@@ -564,6 +564,8 @@ class ExtHostCommentController implements vscode.CommentController {
 		this._threads.forEach(value => {
 			value.dispose();
 		});
+
+		this._proxy.$unregisterCommentController(this.handle);
 	}
 }
 
diff --git a/src/vs/workbench/contrib/comments/electron-browser/commentService.ts b/src/vs/workbench/contrib/comments/electron-browser/commentService.ts
index 61db44b3a09d8ef97efe8af1d699e51f44445d74..582e8adbbc83d58beb017760e95b696827dc3bf0 100644
--- a/src/vs/workbench/contrib/comments/electron-browser/commentService.ts
+++ b/src/vs/workbench/contrib/comments/electron-browser/commentService.ts
@@ -45,6 +45,7 @@ export interface ICommentService {
 	setWorkspaceComments(owner: string, commentsByResource: CommentThread[]): void;
 	removeWorkspaceComments(owner: string): void;
 	registerCommentController(owner: string, commentControl: MainThreadCommentController): void;
+	unregisterCommentController(owner: string): void;
 	registerDataProvider(owner: string, commentProvider: DocumentCommentProvider): void;
 	unregisterDataProvider(owner: string): void;
 	updateComments(ownerId: string, event: CommentThreadChangedEvent): void;
@@ -133,6 +134,11 @@ export class CommentService extends Disposable implements ICommentService {
 		this._onDidSetDataProvider.fire();
 	}
 
+	unregisterCommentController(owner: string): void {
+		this._commentControls.delete(owner);
+		this._onDidDeleteDataProvider.fire(owner);
+	}
+
 	registerDataProvider(owner: string, commentProvider: DocumentCommentProvider): void {
 		this._commentProviders.set(owner, commentProvider);
 		this._onDidSetDataProvider.fire();