diff --git a/packages/core/types/index.d.ts b/packages/core/types/index.d.ts
index ac44d69..889ef28 100644
--- a/packages/core/types/index.d.ts
+++ b/packages/core/types/index.d.ts
@@ -26,7 +26,7 @@ interface MiddlewareAPI<D extends Dispatch = Dispatch, S = any> {
 }
 
 export interface Middleware<_DispatchExt = {}, S = any, D extends Dispatch = Dispatch> {
-  (api: MiddlewareAPI<D, S>): (next: (action: unknown) => unknown) => (action: unknown) => unknown
+  (api: MiddlewareAPI<D, S>): (next: (action: AnyAction) => unknown) => (action: unknown) => unknown
 }
 
 /**
diff --git a/packages/core/types/ts3.6/index.d.ts b/packages/core/types/ts3.6/index.d.ts
index 3f4e107..d00b9d9 100644
--- a/packages/core/types/ts3.6/index.d.ts
+++ b/packages/core/types/ts3.6/index.d.ts
@@ -25,7 +25,7 @@ interface MiddlewareAPI<D extends Dispatch = Dispatch, S = any> {
 }
 
 export interface Middleware<_DispatchExt = {}, S = any, D extends Dispatch = Dispatch> {
-  (api: MiddlewareAPI<D, S>): (next: (action: unknown) => unknown) => (action: unknown) => unknown
+  (api: MiddlewareAPI<D, S>): (next: (action: AnyAction) => unknown) => (action: unknown) => unknown
 }
 
 /**