diff --git a/src/vs/vscode.proposed.d.ts b/src/vs/vscode.proposed.d.ts
index c1b069e85a8..a32810ebda4 100644
--- a/src/vs/vscode.proposed.d.ts
+++ b/src/vs/vscode.proposed.d.ts
@@ -1055,6 +1055,15 @@ declare module 'vscode' {
 	}
 	//#endregion
 
+	//#region Alex - extensions.all change event
+	export namespace extensions {
+		/**
+		 * An event which fires when `extensions.all` changes.
+		 */
+		export const onDidChange: Event<void>;
+	}
+	//#endregion
+
 	//#region Tree View
 
 	export interface TreeView<T> {
diff --git a/src/vs/workbench/api/node/extHost.api.impl.ts b/src/vs/workbench/api/node/extHost.api.impl.ts
index 249c88fa891..ebdf93c02d4 100644
--- a/src/vs/workbench/api/node/extHost.api.impl.ts
+++ b/src/vs/workbench/api/node/extHost.api.impl.ts
@@ -272,6 +272,9 @@ export function createApiFactory(
 			},
 			get all(): Extension<any>[] {
 				return extensionRegistry.getAllExtensionDescriptions().map((desc) => new Extension(extensionService, desc));
+			},
+			get onDidChange() {
+				return extensionRegistry.onDidChange;
 			}
 		};
 
diff --git a/src/vs/workbench/services/extensions/node/extensionDescriptionRegistry.ts b/src/vs/workbench/services/extensions/node/extensionDescriptionRegistry.ts
index ad385a196c9..3eddf8c90ed 100644
--- a/src/vs/workbench/services/extensions/node/extensionDescriptionRegistry.ts
+++ b/src/vs/workbench/services/extensions/node/extensionDescriptionRegistry.ts
@@ -5,8 +5,12 @@
 
 import { IExtensionDescription } from 'vs/workbench/services/extensions/common/extensions';
 import { ExtensionIdentifier } from 'vs/platform/extensions/common/extensions';
+import { Emitter } from 'vs/base/common/event';
 
 export class ExtensionDescriptionRegistry {
+	private readonly _onDidChange = new Emitter<void>();
+	public readonly onDidChange = this._onDidChange.event;
+
 	private _extensionDescriptions: IExtensionDescription[];
 	private _extensionsMap: Map<string, IExtensionDescription>;
 	private _extensionsArr: IExtensionDescription[];
@@ -53,6 +57,7 @@ export class ExtensionDescriptionRegistry {
 		extensionIds.forEach(extensionId => toKeep.add(ExtensionIdentifier.toKey(extensionId)));
 		this._extensionDescriptions = this._extensionDescriptions.filter(extension => toKeep.has(ExtensionIdentifier.toKey(extension.identifier)));
 		this._initialize();
+		this._onDidChange.fire(undefined);
 	}
 
 	public deltaExtensions(toAdd: IExtensionDescription[], toRemove: ExtensionIdentifier[]) {
@@ -61,6 +66,7 @@ export class ExtensionDescriptionRegistry {
 		toRemove.forEach(extensionId => toRemoveSet.add(ExtensionIdentifier.toKey(extensionId)));
 		this._extensionDescriptions = this._extensionDescriptions.filter(extension => !toRemoveSet.has(ExtensionIdentifier.toKey(extension.identifier)));
 		this._initialize();
+		this._onDidChange.fire(undefined);
 	}
 
 	public containsActivationEvent(activationEvent: string): boolean {