diff --git a/src/vs/workbench/api/node/extHost.api.impl.ts b/src/vs/workbench/api/node/extHost.api.impl.ts
index a69e5e34be1..d368888e620 100644
--- a/src/vs/workbench/api/node/extHost.api.impl.ts
+++ b/src/vs/workbench/api/node/extHost.api.impl.ts
@@ -54,7 +54,6 @@ import { ExtHostFileSystem } from 'vs/workbench/api/node/extHostFileSystem';
 import { ExtHostDecorations } from 'vs/workbench/api/node/extHostDecorations';
 import { toGlobPattern, toLanguageSelector } from 'vs/workbench/api/node/extHostTypeConverters';
 import { ExtensionActivatedByAPI } from 'vs/workbench/api/node/extHostExtensionActivator';
-import { isFalsyOrEmpty } from 'vs/base/common/arrays';
 import { OverviewRulerLane } from 'vs/editor/common/model';
 import { ExtHostLogService } from 'vs/workbench/api/node/extHostLogService';
 import { ExtHostWebviews } from 'vs/workbench/api/node/extHostWebview';
@@ -164,28 +163,6 @@ export function createApiFactory(
 			};
 		})();
 
-		if (!isFalsyOrEmpty(product.extensionAllowedProposedApi)
-			&& product.extensionAllowedProposedApi.indexOf(extension.id) >= 0
-		) {
-			// fast lane -> proposed api is available to all extensions
-			// that are listed in product.json-files
-			extension.enableProposedApi = true;
-
-		} else if (extension.enableProposedApi && !extension.isBuiltin) {
-			if (
-				!initData.environment.enableProposedApiForAll &&
-				initData.environment.enableProposedApiFor.indexOf(extension.id) < 0
-			) {
-				extension.enableProposedApi = false;
-				console.error(`Extension '${extension.id} cannot use PROPOSED API (must started out of dev or enabled via --enable-proposed-api)`);
-
-			} else {
-				// proposed api is available when developing or when an extension was explicitly
-				// spelled out via a command line argument
-				console.warn(`Extension '${extension.id}' uses PROPOSED API which is subject to change and removal without notice.`);
-			}
-		}
-
 		// namespace: commands
 		const commands: typeof vscode.commands = {
 			registerCommand(id: string, command: <T>(...args: any[]) => T | Thenable<T>, thisArgs?: any): vscode.Disposable {
diff --git a/src/vs/workbench/api/node/extHost.protocol.ts b/src/vs/workbench/api/node/extHost.protocol.ts
index f18f37f7e78..6bd721a9ec9 100644
--- a/src/vs/workbench/api/node/extHost.protocol.ts
+++ b/src/vs/workbench/api/node/extHost.protocol.ts
@@ -52,8 +52,6 @@ import { TaskExecutionDTO, TaskDTO, TaskHandleDTO } from 'vs/workbench/api/share
 
 export interface IEnvironment {
 	isExtensionDevelopmentDebug: boolean;
-	enableProposedApiForAll: boolean;
-	enableProposedApiFor: string | string[];
 	appRoot: string;
 	appSettingsHome: string;
 	disableExtensions: boolean;
diff --git a/src/vs/workbench/services/extensions/electron-browser/extensionHost.ts b/src/vs/workbench/services/extensions/electron-browser/extensionHost.ts
index c57272a6b22..ad9aab56112 100644
--- a/src/vs/workbench/services/extensions/electron-browser/extensionHost.ts
+++ b/src/vs/workbench/services/extensions/electron-browser/extensionHost.ts
@@ -371,10 +371,7 @@ export class ExtensionHostProcessWorker {
 					appSettingsHome: this._environmentService.appSettingsHome,
 					disableExtensions: this._environmentService.disableExtensions,
 					extensionDevelopmentPath: this._environmentService.extensionDevelopmentPath,
-					extensionTestsPath: this._environmentService.extensionTestsPath,
-					// globally disable proposed api when built and not insiders developing extensions
-					enableProposedApiForAll: !this._environmentService.isBuilt || (!!this._environmentService.extensionDevelopmentPath && product.nameLong.indexOf('Insiders') >= 0),
-					enableProposedApiFor: this._environmentService.args['enable-proposed-api'] || []
+					extensionTestsPath: this._environmentService.extensionTestsPath
 				},
 				workspace: this._contextService.getWorkbenchState() === WorkbenchState.EMPTY ? null : <IWorkspaceData>this._contextService.getWorkspace(),
 				extensions: extensionDescriptions,
diff --git a/src/vs/workbench/services/extensions/electron-browser/extensionService.ts b/src/vs/workbench/services/extensions/electron-browser/extensionService.ts
index ec7847ca19b..7fb1c10edd1 100644
--- a/src/vs/workbench/services/extensions/electron-browser/extensionService.ts
+++ b/src/vs/workbench/services/extensions/electron-browser/extensionService.ts
@@ -41,6 +41,7 @@ import product from 'vs/platform/node/product';
 import * as strings from 'vs/base/common/strings';
 import { RPCProtocol } from 'vs/workbench/services/extensions/node/rpcProtocol';
 import { INotificationService, Severity } from 'vs/platform/notification/common/notification';
+import { isFalsyOrEmpty } from 'vs/base/common/arrays';
 
 let _SystemExtensionsRoot: string = null;
 function getSystemExtensionsRoot(): string {
@@ -497,7 +498,7 @@ export class ExtensionService extends Disposable implements IExtensionService {
 
 	private _scanAndHandleExtensions(): void {
 
-		this._getRuntimeExtension()
+		this._getRuntimeExtensions()
 			.then(runtimeExtensons => {
 				this._registry = new ExtensionDescriptionRegistry(runtimeExtensons);
 
@@ -522,7 +523,7 @@ export class ExtensionService extends Disposable implements IExtensionService {
 			});
 	}
 
-	private _getRuntimeExtension(): TPromise<IExtensionDescription[]> {
+	private _getRuntimeExtensions(): TPromise<IExtensionDescription[]> {
 		const log = new Logger((severity, source, message) => {
 			this._logOrShowMessage(severity, this._isDev ? messageWithSource2(source, message) : message);
 		});
@@ -586,7 +587,36 @@ export class ExtensionService extends Disposable implements IExtensionService {
 							return runtimeExtensions;
 						}
 					});
-			});
+			}).then(extensions => this._updateEnableProposedApi(extensions));
+	}
+
+	private _updateEnableProposedApi(extensions: IExtensionDescription[]): IExtensionDescription[] {
+		const enableProposedApiForAll = !this._environmentService.isBuilt || (!!this._environmentService.extensionDevelopmentPath && product.nameLong.indexOf('Insiders') >= 0);
+		const enableProposedApiFor = this._environmentService.args['enable-proposed-api'] || [];
+		for (const extension of extensions) {
+			if (!isFalsyOrEmpty(product.extensionAllowedProposedApi)
+				&& product.extensionAllowedProposedApi.indexOf(extension.id) >= 0
+			) {
+				// fast lane -> proposed api is available to all extensions
+				// that are listed in product.json-files
+				extension.enableProposedApi = true;
+
+			} else if (extension.enableProposedApi && !extension.isBuiltin) {
+				if (
+					!enableProposedApiForAll &&
+					enableProposedApiFor.indexOf(extension.id) < 0
+				) {
+					extension.enableProposedApi = false;
+					console.error(`Extension '${extension.id} cannot use PROPOSED API (must started out of dev or enabled via --enable-proposed-api)`);
+
+				} else {
+					// proposed api is available when developing or when an extension was explicitly
+					// spelled out via a command line argument
+					console.warn(`Extension '${extension.id}' uses PROPOSED API which is subject to change and removal without notice.`);
+				}
+			}
+		}
+		return extensions;
 	}
 
 	private _handleExtensionPointMessage(msg: IMessage) {