diff --git a/src/vs/vscode.d.ts b/src/vs/vscode.d.ts
index a647bda170c..53b0914085c 100644
--- a/src/vs/vscode.d.ts
+++ b/src/vs/vscode.d.ts
@@ -7375,7 +7375,7 @@ declare module 'vscode' {
 	 */
 	export namespace languages {
 
-		export function changeLanguage(documentUri: Uri, languageId: string): Thenable<void>;
+		export function changeLanguage(document: TextDocument, languageId: string): Thenable<void>;
 
 		/**
 		 * Return the identifiers of all known languages.
diff --git a/src/vs/workbench/api/node/extHost.api.impl.ts b/src/vs/workbench/api/node/extHost.api.impl.ts
index 05932119437..ac686a4878f 100644
--- a/src/vs/workbench/api/node/extHost.api.impl.ts
+++ b/src/vs/workbench/api/node/extHost.api.impl.ts
@@ -258,8 +258,8 @@ export function createApiFactory(
 			getLanguages(): TPromise<string[]> {
 				return extHostLanguages.getLanguages();
 			},
-			changeLanguage(documentUri: vscode.Uri, languageId: string): TPromise<void> {
-				return extHostLanguages.changeLanguage(documentUri, languageId);
+			changeLanguage(document: vscode.TextDocument, languageId: string): TPromise<void> {
+				return extHostLanguages.changeLanguage(document.uri, languageId);
 			},
 			match(selector: vscode.DocumentSelector, document: vscode.TextDocument): number {
 				return score(typeConverters.LanguageSelector.from(selector), document.uri, document.languageId, true);