diff --git a/node/node.d.ts b/node/node.d.ts
index 62eed025af..9ec03907ba 100644
--- a/node/node.d.ts
+++ b/node/node.d.ts
@@ -762,13 +762,15 @@ declare module "fs" {
     export function unlinkSync(path: string): void;
     export function rmdir(path: string, callback?: Function): void;
     export function rmdirSync(path: string): void;
-    export function mkdir(path: string, mode?: string, callback?: Function): void;
+    export function mkdir(path: string, callback?: Function): void;
+    export function mkdir(path: string, mode: string, callback?: Function): void;
     export function mkdirSync(path: string, mode?: string): void;
     export function readdir(path: string, callback?: (err: Error, files: string[]) => void): void;
     export function readdirSync(path: string): string[];
     export function close(fd: string, callback?: Function): void;
     export function closeSync(fd: string): void;
-    export function open(path: string, flags: string, mode?: string, callback?: (err: Error, fd: string) =>any): void;
+    export function open(path: string, flags: string, callback?: (err: Error, fd: string) => any): void;
+    export function open(path: string, flags: string, mode: string, callback?: (err: Error, fd: string) => any): void;
     export function openSync(path: string, flags: string, mode?: string): void;
     export function utimes(path: string, atime: number, mtime: number, callback?: Function): void;
     export function utimesSync(path: string, atime: number, mtime: number): void;