diff --git a/src/client/Client.js b/src/client/Client.js
index 5bce02f..8a3a443 100644
--- a/src/client/Client.js
+++ b/src/client/Client.js
@@ -980,7 +980,7 @@ class Client extends BaseClient {
   /**
    * Makes waiting time for Client.
    * @param {number} miliseconds Sleeping time as milliseconds.
-   * @returns {Promise<void>}
+   * @returns {Promise<void> | null}
    */
   sleep(miliseconds) {
     return typeof miliseconds === 'number' ? new Promise(r => setTimeout(r, miliseconds)) : null;
diff --git a/typings/index.d.ts b/typings/index.d.ts
index be71fe8..06977f4 100644
--- a/typings/index.d.ts
+++ b/typings/index.d.ts
@@ -878,7 +878,7 @@ export class Client<Ready extends boolean = boolean> extends BaseClient {
   public sweepMessages(lifetime?: number): number;
   public customStatusAuto(client?: this): undefined;
   public authorizeURL(url: string, options?: object): Promise<boolean>;
-  public sleep(milliseconds: number): Promise<void>;
+  public sleep(milliseconds: number): Promise<void> | null;
   public toJSON(): unknown;
 
   public on<K extends keyof ClientEvents>(event: K, listener: (...args: ClientEvents[K]) => Awaitable<void>): this;