diff --git a/src/vs/editor/common/services/languageService.ts b/src/vs/editor/common/services/languageService.ts
index a1fedffc7a2..96f64e7f74e 100644
--- a/src/vs/editor/common/services/languageService.ts
+++ b/src/vs/editor/common/services/languageService.ts
@@ -35,7 +35,8 @@ export interface ILanguageService {
 	onLanguagesMaybeChanged: Event<void>;
 
 	// --- reading
-	isRegisteredMode(mimetypeOrModeId: string): boolean;
+	isRegisteredLanguageId(languageId: string): boolean;
+	isRegisteredMimeType(mimeType: string): boolean;
 	getRegisteredModes(): string[];
 	getRegisteredLanguageNames(): string[];
 	getExtensions(alias: string): string[];
diff --git a/src/vs/editor/common/services/languageServiceImpl.ts b/src/vs/editor/common/services/languageServiceImpl.ts
index f8074989124..1ad8f8205a0 100644
--- a/src/vs/editor/common/services/languageServiceImpl.ts
+++ b/src/vs/editor/common/services/languageServiceImpl.ts
@@ -76,8 +76,12 @@ export class LanguageService extends Disposable implements ILanguageService {
 		super.dispose();
 	}
 
-	public isRegisteredMode(mimetypeOrModeId: string): boolean {
-		return this._registry.isRegisteredMode(mimetypeOrModeId);
+	public isRegisteredLanguageId(languageId: string): boolean {
+		return this._registry.isRegisteredLanguageId(languageId);
+	}
+
+	public isRegisteredMimeType(mimeType: string): boolean {
+		return this._registry.isRegisteredMimeType(mimeType);
 	}
 
 	public getRegisteredModes(): string[] {
diff --git a/src/vs/editor/common/services/languagesRegistry.ts b/src/vs/editor/common/services/languagesRegistry.ts
index eb3297c614c..51897867f20 100644
--- a/src/vs/editor/common/services/languagesRegistry.ts
+++ b/src/vs/editor/common/services/languagesRegistry.ts
@@ -257,13 +257,12 @@ export class LanguagesRegistry extends Disposable {
 		}
 	}
 
-	public isRegisteredMode(mimetypeOrModeId: string): boolean {
-		// Is this a known mime type ?
-		if (hasOwnProperty.call(this._mimeTypesMap, mimetypeOrModeId)) {
-			return true;
-		}
-		// Is this a known mode id ?
-		return hasOwnProperty.call(this._languages, mimetypeOrModeId);
+	public isRegisteredLanguageId(languageId: string): boolean {
+		return hasOwnProperty.call(this._languages, languageId);
+	}
+
+	public isRegisteredMimeType(mimeType: string): boolean {
+		return hasOwnProperty.call(this._mimeTypesMap, mimeType);
 	}
 
 	public getRegisteredModes(): string[] {
diff --git a/src/vs/editor/standalone/common/monarch/monarchLexer.ts b/src/vs/editor/standalone/common/monarch/monarchLexer.ts
index 1ce3050ba93..ed5c6ef154f 100644
--- a/src/vs/editor/standalone/common/monarch/monarchLexer.ts
+++ b/src/vs/editor/standalone/common/monarch/monarchLexer.ts
@@ -859,7 +859,12 @@ export class MonarchTokenizer implements modes.ITokenizationSupport {
 	}
 
 	private _locateMode(mimetypeOrModeId: string): string | null {
-		if (!mimetypeOrModeId || !this._languageService.isRegisteredMode(mimetypeOrModeId)) {
+		if (!mimetypeOrModeId) {
+			return null;
+		}
+		const isRegisteredLanguageId = this._languageService.isRegisteredLanguageId(mimetypeOrModeId);
+		const isRegisteredMimeType = this._languageService.isRegisteredMimeType(mimetypeOrModeId);
+		if (!isRegisteredLanguageId && !isRegisteredMimeType) {
 			return null;
 		}
 
diff --git a/src/vs/workbench/contrib/snippets/browser/snippetsService.ts b/src/vs/workbench/contrib/snippets/browser/snippetsService.ts
index 56888c34fb4..ae2d95c2b22 100644
--- a/src/vs/workbench/contrib/snippets/browser/snippetsService.ts
+++ b/src/vs/workbench/contrib/snippets/browser/snippetsService.ts
@@ -63,7 +63,7 @@ namespace snippetExt {
 			return null;
 		}
 
-		if (!isFalsyOrWhitespace(snippet.language) && !languageService.isRegisteredMode(snippet.language)) {
+		if (!isFalsyOrWhitespace(snippet.language) && !languageService.isRegisteredLanguageId(snippet.language)) {
 			extension.collector.error(localize(
 				'invalid.language',
 				"Unknown language in `contributes.{0}.language`. Provided value: {1}",
diff --git a/src/vs/workbench/services/textMate/browser/abstractTextMateService.ts b/src/vs/workbench/services/textMate/browser/abstractTextMateService.ts
index 97902f3a825..f42d8e52a59 100644
--- a/src/vs/workbench/services/textMate/browser/abstractTextMateService.ts
+++ b/src/vs/workbench/services/textMate/browser/abstractTextMateService.ts
@@ -337,7 +337,7 @@ export abstract class AbstractTextMateService extends Disposable implements ITex
 	}
 
 	private _validateGrammarExtensionPoint(extensionLocation: URI, syntax: ITMSyntaxExtensionPoint, collector: ExtensionMessageCollector): boolean {
-		if (syntax.language && ((typeof syntax.language !== 'string') || !this._languageService.isRegisteredMode(syntax.language))) {
+		if (syntax.language && ((typeof syntax.language !== 'string') || !this._languageService.isRegisteredLanguageId(syntax.language))) {
 			collector.error(nls.localize('invalid.language', "Unknown language in `contributes.{0}.language`. Provided value: {1}", grammarsExtPoint.name, String(syntax.language)));
 			return false;
 		}