diff --git a/src/vs/platform/extensionManagement/common/extensionGalleryService.ts b/src/vs/platform/extensionManagement/common/extensionGalleryService.ts
index 6f04a76edb65e..3515dea44640b 100644
--- a/src/vs/platform/extensionManagement/common/extensionGalleryService.ts
+++ b/src/vs/platform/extensionManagement/common/extensionGalleryService.ts
@@ -584,7 +584,14 @@ abstract class AbstractExtensionGalleryService implements IExtensionGalleryServi
 		const config = productService.extensionsGallery;
 		this.extensionsGalleryUrl = config && config.serviceUrl;
 		this.extensionsControlUrl = config && config.controlUrl;
-		this.commonHeadersPromise = resolveMarketplaceHeaders(productService.version, productService, this.environmentService, this.configurationService, this.fileService, storageService);
+		this.commonHeadersPromise = resolveMarketplaceHeaders(
+			productService.version,
+			productService,
+			this.environmentService,
+			this.configurationService,
+			this.fileService,
+			storageService,
+			this.telemetryService);
 	}
 
 	private api(path = ''): string {
@@ -928,7 +935,7 @@ abstract class AbstractExtensionGalleryService implements IExtensionGalleryServi
 			'Content-Type': 'application/json',
 			'Accept': 'application/json;api-version=3.0-preview.1',
 			'Accept-Encoding': 'gzip',
-			'Content-Length': String(data.length)
+			'Content-Length': String(data.length),
 		};
 
 		const startTime = new Date().getTime();
diff --git a/src/vs/platform/extensionManagement/test/common/extensionGalleryService.test.ts b/src/vs/platform/extensionManagement/test/common/extensionGalleryService.test.ts
index 4312de805f8a0..7dcb41d56bf50 100644
--- a/src/vs/platform/extensionManagement/test/common/extensionGalleryService.test.ts
+++ b/src/vs/platform/extensionManagement/test/common/extensionGalleryService.test.ts
@@ -23,6 +23,7 @@ import { resolveMarketplaceHeaders } from 'vs/platform/externalServices/common/m
 import { InMemoryStorageService, IStorageService } from 'vs/platform/storage/common/storage';
 import { TelemetryConfiguration, TELEMETRY_SETTING_ID } from 'vs/platform/telemetry/common/telemetry';
 import { TargetPlatform } from 'vs/platform/extensions/common/extensions';
+import { NullTelemetryService } from 'vs/platform/telemetry/common/telemetryUtils';
 
 class EnvironmentServiceMock extends mock<IEnvironmentService>() {
 	override readonly serviceMachineIdResource: URI;
@@ -52,9 +53,9 @@ suite('Extension Gallery Service', () => {
 	teardown(() => disposables.clear());
 
 	test('marketplace machine id', async () => {
-		const headers = await resolveMarketplaceHeaders(product.version, productService, environmentService, configurationService, fileService, storageService);
+		const headers = await resolveMarketplaceHeaders(product.version, productService, environmentService, configurationService, fileService, storageService, NullTelemetryService);
 		assert.ok(isUUID(headers['X-Market-User-Id']));
-		const headers2 = await resolveMarketplaceHeaders(product.version, productService, environmentService, configurationService, fileService, storageService);
+		const headers2 = await resolveMarketplaceHeaders(product.version, productService, environmentService, configurationService, fileService, storageService, NullTelemetryService);
 		assert.strictEqual(headers['X-Market-User-Id'], headers2['X-Market-User-Id']);
 	});
 
diff --git a/src/vs/platform/externalServices/common/marketplace.ts b/src/vs/platform/externalServices/common/marketplace.ts
index 6d2c25ab86d3c..5923e1cd8e880 100644
--- a/src/vs/platform/externalServices/common/marketplace.ts
+++ b/src/vs/platform/externalServices/common/marketplace.ts
@@ -10,17 +10,26 @@ import { getServiceMachineId } from 'vs/platform/externalServices/common/service
 import { IFileService } from 'vs/platform/files/common/files';
 import { IProductService } from 'vs/platform/product/common/productService';
 import { IStorageService } from 'vs/platform/storage/common/storage';
-import { TelemetryLevel } from 'vs/platform/telemetry/common/telemetry';
+import { ITelemetryService, TelemetryLevel } from 'vs/platform/telemetry/common/telemetry';
 import { getTelemetryLevel, supportsTelemetry } from 'vs/platform/telemetry/common/telemetryUtils';
 
-export async function resolveMarketplaceHeaders(version: string, productService: IProductService, environmentService: IEnvironmentService, configurationService: IConfigurationService, fileService: IFileService, storageService: IStorageService | undefined): Promise<IHeaders> {
+export async function resolveMarketplaceHeaders(version: string,
+	productService: IProductService,
+	environmentService: IEnvironmentService,
+	configurationService: IConfigurationService,
+	fileService: IFileService,
+	storageService: IStorageService | undefined,
+	telemetryService: ITelemetryService): Promise<IHeaders> {
 	const headers: IHeaders = {
 		'X-Market-Client-Id': `VSCode ${version}`,
 		'User-Agent': `VSCode ${version} (${productService.nameShort})`
 	};
 	const uuid = await getServiceMachineId(environmentService, fileService, storageService);
+	const { sessionId } = await telemetryService.getTelemetryInfo();
+
 	if (supportsTelemetry(productService, environmentService) && getTelemetryLevel(configurationService) === TelemetryLevel.USAGE) {
 		headers['X-Market-User-Id'] = uuid;
+		headers['VSCode-SessionId'] = sessionId;
 	}
 	return headers;
 }
diff --git a/src/vs/platform/windows/electron-main/window.ts b/src/vs/platform/windows/electron-main/window.ts
index 02524b2235bf5..fcc8c93ee47ee 100644
--- a/src/vs/platform/windows/electron-main/window.ts
+++ b/src/vs/platform/windows/electron-main/window.ts
@@ -542,7 +542,14 @@ export class CodeWindow extends Disposable implements ICodeWindow {
 	private marketplaceHeadersPromise: Promise<object> | undefined;
 	private getMarketplaceHeaders(): Promise<object> {
 		if (!this.marketplaceHeadersPromise) {
-			this.marketplaceHeadersPromise = resolveMarketplaceHeaders(this.productService.version, this.productService, this.environmentMainService, this.configurationService, this.fileService, this.applicationStorageMainService);
+			this.marketplaceHeadersPromise = resolveMarketplaceHeaders(
+				this.productService.version,
+				this.productService,
+				this.environmentMainService,
+				this.configurationService,
+				this.fileService,
+				this.applicationStorageMainService,
+				this.telemetryService);
 		}
 
 		return this.marketplaceHeadersPromise;