diff --git a/src/vs/base/common/types.ts b/src/vs/base/common/types.ts
index 42eea76fe40..634c6e5143a 100644
--- a/src/vs/base/common/types.ts
+++ b/src/vs/base/common/types.ts
@@ -258,3 +258,19 @@ export type Dto<T> = { [K in keyof T]: T[K] extends URI
 	: T[K] extends Function
 	? never
 	: UriDto<T[K]> };
+
+
+export function NotImplementedProxy<T>(name: string): { new(): T } {
+	return <any>class {
+		constructor() {
+			return new Proxy({}, {
+				get(target: any, prop: PropertyKey) {
+					if (target[prop]) {
+						return target[prop];
+					}
+					throw new Error(`Not Implemented: ${name}->${String(prop)}`);
+				}
+			});
+		}
+	};
+}
diff --git a/src/vs/workbench/services/extensions/worker/extHost.services.ts b/src/vs/workbench/services/extensions/worker/extHost.services.ts
index 90568629458..100864519dc 100644
--- a/src/vs/workbench/services/extensions/worker/extHost.services.ts
+++ b/src/vs/workbench/services/extensions/worker/extHost.services.ts
@@ -18,11 +18,11 @@ import { IExtensionStoragePaths } from 'vs/workbench/api/common/extHostStoragePa
 import { IExtHostExtensionService } from 'vs/workbench/api/common/extHostExtensionService';
 import { IExtHostStorage, ExtHostStorage } from 'vs/workbench/api/common/extHostStorage';
 import { ExtHostExtensionService } from 'vs/workbench/api/worker/extHostExtensionService';
-import { ServiceIdentifier } from 'vs/platform/instantiation/common/instantiation';
 import { ILogService } from 'vs/platform/log/common/log';
 import { ExtHostLogService } from 'vs/workbench/api/worker/extHostLogService';
 import { IExtHostTunnelService, ExtHostTunnelService } from 'vs/workbench/api/common/extHostTunnelService';
 import { IExtHostApiDeprecationService, ExtHostApiDeprecationService, } from 'vs/workbench/api/common/extHostApiDeprecationService';
+import { NotImplementedProxy } from 'vs/base/common/types';
 
 // register singleton services
 registerSingleton(ILogService, ExtHostLogService);
@@ -38,22 +38,7 @@ registerSingleton(IExtHostExtensionService, ExtHostExtensionService);
 registerSingleton(IExtHostSearch, ExtHostSearch);
 registerSingleton(IExtHostTunnelService, ExtHostTunnelService);
 
-// register services that only throw errors
-function NotImplementedProxy<T>(name: ServiceIdentifier<T>): { new(): T } {
-	return <any>class {
-		constructor() {
-			return new Proxy({}, {
-				get(target: any, prop: PropertyKey) {
-					if (target[prop]) {
-						return target[prop];
-					}
-					throw new Error(`Not Implemented: ${name}->${String(prop)}`);
-				}
-			});
-		}
-	};
-}
 registerSingleton(IExtHostTerminalService, WorkerExtHostTerminalService);
 registerSingleton(IExtHostTask, WorkerExtHostTask);
 registerSingleton(IExtHostDebugService, WorkerExtHostDebugService);
-registerSingleton(IExtensionStoragePaths, class extends NotImplementedProxy(IExtensionStoragePaths) { whenReady = Promise.resolve(); });
+registerSingleton(IExtensionStoragePaths, class extends NotImplementedProxy<IExtensionStoragePaths>(String(IExtensionStoragePaths)) { whenReady = Promise.resolve(); });