diff --git a/types/rwlock/index.d.ts b/types/rwlock/index.d.ts
index 029c9d3d2b..a7611f22da 100644
--- a/types/rwlock/index.d.ts
+++ b/types/rwlock/index.d.ts
@@ -10,27 +10,21 @@ declare class ReadWriteGeneric<T> {
   writeLock(key: string, callback: T, options?: ReadWriteLock.Options): void;
 }
 declare namespace ReadWriteLock {
-  interface Release {
-    (): void;
-  }
+  type Release = () => void;
 
-  interface Callback {
-    (release: Release): void;
-  }
+  type Callback = (release: Release) => void;
 
-  interface AsyncCallback {
-    (err: Error, release: Release): void;
-  }
+  type AsyncCallback = (err: Error, release: Release) => void;
 
   interface Options {
     scope?: any;
     timeout?: number;
-    timeoutCallback?: () => void;
+    timeoutCallback(): void;
   }
 }
 
-declare class ReadWriteLock extends ReadWriteGeneric<ReadWriteLock.Callback>{
+declare class ReadWriteLock extends ReadWriteGeneric<ReadWriteLock.Callback> {
   constructor();
   async: ReadWriteGeneric<ReadWriteLock.AsyncCallback>;
 }
-export = ReadWriteLock
\ No newline at end of file
+export = ReadWriteLock;
diff --git a/types/rwlock/rwlock-tests.ts b/types/rwlock/rwlock-tests.ts
index 411733220b..8e2f210164 100644
--- a/types/rwlock/rwlock-tests.ts
+++ b/types/rwlock/rwlock-tests.ts
@@ -1,7 +1,7 @@
 // Original test file https://github.com/71104/rwlock/blob/master/test/all.js
 import * as ReadWriteLock from 'rwlock';
 
-var lock = new ReadWriteLock();
-lock.readLock(function (release) {
+const lock = new ReadWriteLock();
+lock.readLock((release) => {
   release();
 });