diff --git a/swig/swig.d.ts b/swig/swig.d.ts
index db2353375..3d4e07df1 100644
--- a/swig/swig.d.ts
+++ b/swig/swig.d.ts
@@ -9,7 +9,7 @@ declare module "swig" {
 	export function init(options: Options): void;
 	export function compileFile(filepath: string): any;
 	export function compile(source: string, options?: Options): any;
-	export function renderFile(pathName: string, locals: any, cb: (err: any, output: string) => void): string;
+	export function renderFile(pathName: string, locals?: any, cb?: (err: any, output: string) => void): string;
 
 	export interface Options {
 		allowErrors?: boolean;