diff --git a/types/redux-promise-middleware/index.d.ts b/types/redux-promise-middleware/index.d.ts
index f52233f704..1317f65ae2 100644
--- a/types/redux-promise-middleware/index.d.ts
+++ b/types/redux-promise-middleware/index.d.ts
@@ -5,4 +5,4 @@
 
 import { Middleware } from 'redux';
 
-export default function promiseMiddleware(config?: { promiseTypeSuffixes: string[] }): Middleware;
+export default function promiseMiddleware(config?: { promiseTypeSuffixes?: string[], promiseTypeSeparator?: string }): Middleware;