diff --git a/src/vs/workbench/api/browser/mainThreadWorkspace.ts b/src/vs/workbench/api/browser/mainThreadWorkspace.ts
index 13d352d9bd4..252fa8e426e 100644
--- a/src/vs/workbench/api/browser/mainThreadWorkspace.ts
+++ b/src/vs/workbench/api/browser/mainThreadWorkspace.ts
@@ -24,6 +24,7 @@ import { INotificationService } from 'vs/platform/notification/common/notificati
 import { withNullAsUndefined } from 'vs/base/common/types';
 import { IFileService } from 'vs/platform/files/common/files';
 import { IRequestService } from 'vs/platform/request/common/request';
+import { checkGlobFileExists } from 'vs/workbench/api/common/shared/workspaceContains';
 
 @extHostNamedCustomer(MainContext.MainThreadWorkspace)
 export class MainThreadWorkspace implements MainThreadWorkspaceShape {
@@ -189,25 +190,7 @@ export class MainThreadWorkspace implements MainThreadWorkspaceShape {
 	}
 
 	$checkExists(folders: readonly UriComponents[], includes: string[], token: CancellationToken): Promise<boolean> {
-		const queryBuilder = this._instantiationService.createInstance(QueryBuilder);
-		const query = queryBuilder.file(folders.map(folder => toWorkspaceFolder(URI.revive(folder))), {
-			_reason: 'checkExists',
-			includePattern: includes.join(', '),
-			expandPatterns: true,
-			exists: true
-		});
-
-		return this._searchService.fileSearch(query, token).then(
-			result => {
-				return !!result.limitHit;
-			},
-			err => {
-				if (!isPromiseCanceledError(err)) {
-					return Promise.reject(err);
-				}
-
-				return false;
-			});
+		return this._instantiationService.invokeFunction((accessor) => checkGlobFileExists(accessor, folders, includes, token));
 	}
 
 	// --- save & edit resources ---
diff --git a/src/vs/workbench/api/common/shared/workspaceContains.ts b/src/vs/workbench/api/common/shared/workspaceContains.ts
index 8a641e241dd..7f883983ea7 100644
--- a/src/vs/workbench/api/common/shared/workspaceContains.ts
+++ b/src/vs/workbench/api/common/shared/workspaceContains.ts
@@ -8,6 +8,10 @@ import { URI, UriComponents } from 'vs/base/common/uri';
 import { CancellationTokenSource, CancellationToken } from 'vs/base/common/cancellation';
 import * as errors from 'vs/base/common/errors';
 import { ExtensionIdentifier, IExtensionDescription } from 'vs/platform/extensions/common/extensions';
+import { IInstantiationService, ServicesAccessor } from 'vs/platform/instantiation/common/instantiation';
+import { QueryBuilder } from 'vs/workbench/contrib/search/common/queryBuilder';
+import { ISearchService } from 'vs/workbench/services/search/common/search';
+import { toWorkspaceFolder } from 'vs/platform/workspace/common/workspace';
 
 const WORKSPACE_CONTAINS_TIMEOUT = 7000;
 
@@ -103,3 +107,32 @@ async function _activateIfGlobPatterns(host: IExtensionActivationHost, extension
 		activate(`workspaceContains:${globPatterns.join(',')}`);
 	}
 }
+
+export function checkGlobFileExists(
+	accessor: ServicesAccessor,
+	folders: readonly UriComponents[],
+	includes: string[],
+	token: CancellationToken,
+): Promise<boolean> {
+	const instantiationService = accessor.get(IInstantiationService);
+	const searchService = accessor.get(ISearchService);
+	const queryBuilder = instantiationService.createInstance(QueryBuilder);
+	const query = queryBuilder.file(folders.map(folder => toWorkspaceFolder(URI.revive(folder))), {
+		_reason: 'checkExists',
+		includePattern: includes.join(', '),
+		expandPatterns: true,
+		exists: true
+	});
+
+	return searchService.fileSearch(query, token).then(
+		result => {
+			return !!result.limitHit;
+		},
+		err => {
+			if (!errors.isPromiseCanceledError(err)) {
+				return Promise.reject(err);
+			}
+
+			return false;
+		});
+}
diff --git a/src/vs/workbench/services/extensions/electron-browser/extensionService.ts b/src/vs/workbench/services/extensions/electron-browser/extensionService.ts
index b149586e303..1438fdeabd4 100644
--- a/src/vs/workbench/services/extensions/electron-browser/extensionService.ts
+++ b/src/vs/workbench/services/extensions/electron-browser/extensionService.ts
@@ -41,6 +41,9 @@ import { Extensions as ActionExtensions, IWorkbenchActionRegistry } from 'vs/wor
 import { getRemoteName } from 'vs/platform/remote/common/remoteHosts';
 import { IRemoteAgentEnvironment } from 'vs/platform/remote/common/remoteAgentEnvironment';
 import { WebWorkerExtensionHost } from 'vs/workbench/services/extensions/browser/webWorkerExtensionHost';
+import { IExtensionActivationHost as IWorkspaceContainsActivationHost, checkGlobFileExists, checkActivateWorkspaceContainsExtension } from 'vs/workbench/api/common/shared/workspaceContains';
+import { IWorkspaceContextService } from 'vs/platform/workspace/common/workspace';
+import { exists } from 'vs/base/node/pfs';
 
 class DeltaExtensionsQueueItem {
 	constructor(
@@ -75,6 +78,7 @@ export class ExtensionService extends AbstractExtensionService implements IExten
 		@IHostService private readonly _hostService: IHostService,
 		@IRemoteExplorerService private readonly _remoteExplorerService: IRemoteExplorerService,
 		@IExtensionGalleryService private readonly _extensionGalleryService: IExtensionGalleryService,
+		@IWorkspaceContextService private readonly _contextService: IWorkspaceContextService,
 	) {
 		super(
 			instantiationService,
@@ -308,6 +312,7 @@ export class ExtensionService extends AbstractExtensionService implements IExten
 
 		let shouldActivate = false;
 		let shouldActivateReason: string | null = null;
+		let hasWorkspaceContains = false;
 		if (Array.isArray(extensionDescription.activationEvents)) {
 			for (let activationEvent of extensionDescription.activationEvents) {
 				// TODO@joao: there's no easy way to contribute this
@@ -329,10 +334,7 @@ export class ExtensionService extends AbstractExtensionService implements IExten
 				}
 
 				if (/^workspaceContains/.test(activationEvent)) {
-					// do not trigger a search, just activate in this case...
-					shouldActivate = true;
-					shouldActivateReason = activationEvent;
-					break;
+					hasWorkspaceContains = true;
 				}
 
 				if (activationEvent === 'onStartupFinished') {
@@ -347,6 +349,24 @@ export class ExtensionService extends AbstractExtensionService implements IExten
 			await Promise.all(
 				this._extensionHostManagers.map(extHostManager => extHostManager.activate(extensionDescription.identifier, { startup: false, extensionId: extensionDescription.identifier, activationEvent: shouldActivateReason! }))
 			).then(() => { });
+		} else if (hasWorkspaceContains) {
+			const workspace = await this._contextService.getCompleteWorkspace();
+			const forceUsingSearch = !!this._environmentService.configuration.remoteAuthority;
+			const host: IWorkspaceContainsActivationHost = {
+				folders: workspace.folders.map(folder => folder.uri),
+				forceUsingSearch: forceUsingSearch,
+				exists: (path) => exists(path),
+				checkExists: (folders, includes, token) => this._instantiationService.invokeFunction((accessor) => checkGlobFileExists(accessor, folders, includes, token))
+			};
+
+			const result = await checkActivateWorkspaceContainsExtension(host, extensionDescription);
+			if (!result) {
+				return;
+			}
+
+			await Promise.all(
+				this._extensionHostManagers.map(extHostManager => extHostManager.activate(extensionDescription.identifier, { startup: false, extensionId: extensionDescription.identifier, activationEvent: result.activationEvent }))
+			).then(() => { });
 		}
 	}