diff --git a/types/ioredis/index.d.ts b/types/ioredis/index.d.ts
index 5c7f334c27..0e348ea430 100644
--- a/types/ioredis/index.d.ts
+++ b/types/ioredis/index.d.ts
@@ -796,7 +796,7 @@ declare namespace IORedis {
 
         ttl(key: KeyType, callback?: (err: Error, res: number) => void): Pipeline;
 
-        pttl(key: KeyType, callback: (err: Error, res: number) => void): Pipeline;
+        pttl(key: KeyType, callback?: (err: Error, res: number) => void): Pipeline;
 
         persist(key: KeyType, callback?: (err: Error, res: 0 | 1) => void): Pipeline;