diff --git a/src/vs/platform/environment/common/environment.ts b/src/vs/platform/environment/common/environment.ts
index 1157e1cb272..3bd6e491236 100644
--- a/src/vs/platform/environment/common/environment.ts
+++ b/src/vs/platform/environment/common/environment.ts
@@ -146,6 +146,7 @@ export interface IEnvironmentService extends IUserHomeProvider {
 	extensionsPath?: string;
 	extensionDevelopmentLocationURI?: URI[];
 	extensionTestsLocationURI?: URI;
+	extensionEnabledProposedApi?: string[] | undefined;
 	logExtensionHostCommunication?: boolean;
 
 	debugExtensionHost: IExtensionHostDebugParams;
diff --git a/src/vs/platform/environment/node/environmentService.ts b/src/vs/platform/environment/node/environmentService.ts
index 55ed6cb34e1..9f518b9729d 100644
--- a/src/vs/platform/environment/node/environmentService.ts
+++ b/src/vs/platform/environment/node/environmentService.ts
@@ -233,6 +233,18 @@ export class EnvironmentService implements IEnvironmentService {
 		return false;
 	}
 
+	get extensionEnabledProposedApi(): string[] | undefined {
+		if (Array.isArray(this.args['enable-proposed-api'])) {
+			return this.args['enable-proposed-api'];
+		}
+
+		if ('enable-proposed-api' in this.args) {
+			return [];
+		}
+
+		return undefined;
+	}
+
 	@memoize
 	get debugExtensionHost(): IExtensionHostDebugParams { return parseExtensionHostPort(this._args, this.isBuilt); }
 	@memoize
diff --git a/src/vs/workbench/services/environment/browser/environmentService.ts b/src/vs/workbench/services/environment/browser/environmentService.ts
index 93e05e6d14a..1b6c7b913c9 100644
--- a/src/vs/workbench/services/environment/browser/environmentService.ts
+++ b/src/vs/workbench/services/environment/browser/environmentService.ts
@@ -69,6 +69,7 @@ interface IExtensionHostDebugEnvironment {
 	isExtensionDevelopment: boolean;
 	extensionDevelopmentLocationURI?: URI[];
 	extensionTestsLocationURI?: URI;
+	extensionEnabledProposedApi?: string[];
 }
 
 export class BrowserWorkbenchEnvironmentService implements IWorkbenchEnvironmentService {
@@ -156,6 +157,14 @@ export class BrowserWorkbenchEnvironmentService implements IWorkbenchEnvironment
 		return this._extensionHostDebugEnvironment.extensionTestsLocationURI;
 	}
 
+	get extensionEnabledProposedApi(): string[] | undefined {
+		if (!this._extensionHostDebugEnvironment) {
+			this._extensionHostDebugEnvironment = this.resolveExtensionHostDebugEnvironment();
+		}
+
+		return this._extensionHostDebugEnvironment.extensionEnabledProposedApi;
+	}
+
 	@memoize
 	get webviewExternalEndpoint(): string {
 		// TODO: get fallback from product.json
@@ -216,6 +225,9 @@ export class BrowserWorkbenchEnvironmentService implements IWorkbenchEnvironment
 						extensionHostDebugEnvironment.params.port = parseInt(value);
 						extensionHostDebugEnvironment.params.break = true;
 						break;
+					case 'enableProposedApi':
+						extensionHostDebugEnvironment.extensionEnabledProposedApi = [];
+						break;
 				}
 			}
 		}
diff --git a/src/vs/workbench/services/extensions/common/abstractExtensionService.ts b/src/vs/workbench/services/extensions/common/abstractExtensionService.ts
index 9d9e4e4d320..c5f788650eb 100644
--- a/src/vs/workbench/services/extensions/common/abstractExtensionService.ts
+++ b/src/vs/workbench/services/extensions/common/abstractExtensionService.ts
@@ -457,12 +457,12 @@ class ProposedApiController {
 		@IProductService productService: IProductService
 	) {
 		// Make enabled proposed API be lowercase for case insensitive comparison
-		this.enableProposedApiFor = (environmentService.args['enable-proposed-api'] || []).map(id => id.toLowerCase());
+		this.enableProposedApiFor = (environmentService.extensionEnabledProposedApi || []).map(id => id.toLowerCase());
 
 		this.enableProposedApiForAll =
 			!environmentService.isBuilt || // always allow proposed API when running out of sources
 			(!!environmentService.extensionDevelopmentLocationURI && productService.quality !== 'stable') || // do not allow proposed API against stable builds when developing an extension
-			(this.enableProposedApiFor.length === 0 && 'enable-proposed-api' in environmentService.args); // always allow proposed API if --enable-proposed-api is provided without extension ID
+			(this.enableProposedApiFor.length === 0 && Array.isArray(environmentService.extensionEnabledProposedApi)); // always allow proposed API if --enable-proposed-api is provided without extension ID
 
 		this.productAllowProposedApi = new Set<string>();
 		if (isNonEmptyArray(productService.extensionAllowedProposedApi)) {
diff --git a/test/integration/browser/src/index.ts b/test/integration/browser/src/index.ts
index 99f40a87fd3..99a66c318f8 100644
--- a/test/integration/browser/src/index.ts
+++ b/test/integration/browser/src/index.ts
@@ -3,12 +3,12 @@
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
 
-import * as  path from 'path';
-import * as  cp from 'child_process';
-import * as  playwright from 'playwright';
-import * as  url from 'url';
-import * as  tmp from 'tmp';
-import * as  rimraf from 'rimraf';
+import * as path from 'path';
+import * as cp from 'child_process';
+import * as playwright from 'playwright';
+import * as url from 'url';
+import * as tmp from 'tmp';
+import * as rimraf from 'rimraf';
 import { URI } from 'vscode-uri';
 import * as kill from 'tree-kill';
 import * as optimistLib from 'optimist';
@@ -44,7 +44,7 @@ async function runTestsInBrowser(browserType: 'chromium' | 'firefox' | 'webkit',
 	const testFilesUri = url.format({ pathname: URI.file(path.resolve(optimist.argv.extensionTestsPath)).path, protocol, host, slashes: true });
 
 	const folderParam = testWorkspaceUri;
-	const payloadParam = `[["extensionDevelopmentPath","${testExtensionUri}"],["extensionTestsPath","${testFilesUri}"]]`;
+	const payloadParam = `[["extensionDevelopmentPath","${testExtensionUri}"],["extensionTestsPath","${testFilesUri}"],["enableProposedApi",""]]`;
 
 	await page.goto(`${endpoint.href}&folder=${folderParam}&payload=${payloadParam}`);