diff --git a/src/vs/workbench/api/common/extHostLanguageFeatures.ts b/src/vs/workbench/api/common/extHostLanguageFeatures.ts
index 8f14bc22f4dfd8b40261a44302e13b0d9cda1d3a..b26a4ef040563da7f43fc6ef5d963c626e540972 100644
--- a/src/vs/workbench/api/common/extHostLanguageFeatures.ts
+++ b/src/vs/workbench/api/common/extHostLanguageFeatures.ts
@@ -32,6 +32,7 @@ import { IdGenerator } from 'vs/base/common/idGenerator';
 import { IExtHostApiDeprecationService } from 'vs/workbench/api/common/extHostApiDeprecationService';
 import { Cache } from './cache';
 import { StopWatch } from 'vs/base/common/stopwatch';
+import { checkProposedApiEnabled } from 'vs/workbench/services/extensions/common/extensions';
 
 // --- adapter
 
@@ -1822,6 +1823,7 @@ export class ExtHostLanguageFeatures implements extHostProtocol.ExtHostLanguageF
 		let result = this._createDisposable(handle);
 
 		if (eventHandle !== undefined) {
+			checkProposedApiEnabled(extension);
 			const subscription = provider.onDidChangeFoldingRanges!(_ => this._proxy.$emitFoldingRangeEvent(eventHandle));
 			result = Disposable.from(result, subscription);
 		}