diff --git a/node/node.d.ts b/node/node.d.ts
index 341b63c469..3c93a9bf30 100644
--- a/node/node.d.ts
+++ b/node/node.d.ts
@@ -727,8 +727,8 @@ declare module "fs" {
     export function renameSync(oldPath: string, newPath: string): void;
     export function truncate(path: string, len: number, callback?: Function): void;
     export function truncateSync(path: string, len: number): void;
-    export function ftruncate(fd: number, len: number, callback?: Function): void;
-    export function ftruncateSync(fd: number, len: number): void;
+    export function ftruncate(fd: string, len: number, callback?: Function): void;
+    export function ftruncateSync(fd: string, len: number): void;
     export function chown(path: string, uid: number, gid: number, callback?: Function): void;
     export function chownSync(path: string, uid: number, gid: number): void;
     export function fchown(fd: string, uid: number, gid: number, callback?: Function): void;