diff --git a/src/tsconfig.strictNullChecks.json b/src/tsconfig.strictNullChecks.json
index 8e7a19f9f78..1e4f1a3dfb4 100644
--- a/src/tsconfig.strictNullChecks.json
+++ b/src/tsconfig.strictNullChecks.json
@@ -511,6 +511,7 @@
 		"./vs/platform/telemetry/common/telemetry.ts",
 		"./vs/platform/telemetry/common/telemetryService.ts",
 		"./vs/platform/telemetry/common/telemetryUtils.ts",
+		"./vs/platform/telemetry/node/appInsightsAppender.ts",
 		"./vs/platform/telemetry/node/commonProperties.ts",
 		"./vs/platform/telemetry/node/telemetryIpc.ts",
 		"./vs/platform/telemetry/node/telemetryNodeUtils.ts",
@@ -592,6 +593,7 @@
 		"./vs/workbench/parts/codeEditor/electron-browser/toggleWordWrap.ts",
 		"./vs/workbench/parts/comments/common/commentModel.ts",
 		"./vs/workbench/parts/comments/electron-browser/commentGlyphWidget.ts",
+		"./vs/workbench/parts/debug/node/telemetryApp.ts",
 		"./vs/workbench/parts/emmet/browser/actions/showEmmetCommands.ts",
 		"./vs/workbench/parts/emmet/browser/emmet.browser.contribution.ts",
 		"./vs/workbench/parts/emmet/electron-browser/actions/expandAbbreviation.ts",
diff --git a/src/vs/platform/telemetry/common/telemetryUtils.ts b/src/vs/platform/telemetry/common/telemetryUtils.ts
index 22b6ed96274..0a2bc0dc06b 100644
--- a/src/vs/platform/telemetry/common/telemetryUtils.ts
+++ b/src/vs/platform/telemetry/common/telemetryUtils.ts
@@ -29,7 +29,7 @@ export const NullTelemetryService = new class implements ITelemetryService {
 
 export interface ITelemetryAppender {
 	log(eventName: string, data: any): void;
-	dispose(): Thenable<any>;
+	dispose(): Thenable<any> | undefined;
 }
 
 export function combinedAppender(...appenders: ITelemetryAppender[]): ITelemetryAppender {
diff --git a/src/vs/platform/telemetry/node/appInsightsAppender.ts b/src/vs/platform/telemetry/node/appInsightsAppender.ts
index 96440af93ec..f88a00de17d 100644
--- a/src/vs/platform/telemetry/node/appInsightsAppender.ts
+++ b/src/vs/platform/telemetry/node/appInsightsAppender.ts
@@ -45,7 +45,7 @@ interface Measurements {
 
 export class AppInsightsAppender implements ITelemetryAppender {
 
-	private _aiClient: appInsights.TelemetryClient;
+	private _aiClient?: appInsights.TelemetryClient;
 
 	constructor(
 		private _eventPrefix: string,
@@ -143,10 +143,10 @@ export class AppInsightsAppender implements ITelemetryAppender {
 		});
 	}
 
-	dispose(): Promise<any> {
+	dispose(): Promise<any> | undefined {
 		if (this._aiClient) {
 			return new Promise(resolve => {
-				this._aiClient.flush({
+				this._aiClient!.flush({
 					callback: () => {
 						// all data flushed
 						this._aiClient = undefined;