diff --git a/types/mz/fs.d.ts b/types/mz/fs.d.ts
index 975850c3ab..ff7222acee 100644
--- a/types/mz/fs.d.ts
+++ b/types/mz/fs.d.ts
@@ -142,7 +142,7 @@ export function stat(path: string | Buffer): Promise<fs.Stats>;
  * `lstat()` is identical to `stat()`, except that if path is a symbolic link, then the link itself
  * is stat-ed, not the file that it refers to.
  */
-export function lstat(path: string | Buffer, callback?: (err: NodeJS.ErrnoException, stats: fs.Stats) => any): void;
+export function lstat(path: string | Buffer, callback: (err: NodeJS.ErrnoException, stats: fs.Stats) => any): void;
 
 /**
  * Asynchronous `lstat(2)`.
@@ -502,4 +502,4 @@ export function access(path: string | Buffer, callback: (err: NodeJS.ErrnoExcept
  * @param path The path to access.
  * @param mode An optional integer that specifies the accessibility checks to be performed.
  */
-export function access(path: string, mode?: number): Promise<void>;
\ No newline at end of file
+export function access(path: string, mode?: number): Promise<void>;