diff --git a/src/types.ts b/src/types.ts
index d990d9a..4cc45c0 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -8,7 +8,7 @@ export type Handler<T = unknown> = (data: T) => void;
 export type HandlerCallback<R> = Handler<Channels[keyof Channels]>;
 
 export interface Pubsub<T extends Record<string, unknown> = {}> {
-  data: Map<any, any>;
+  data: Map<keyof T, HandlerCallback<T>[]>;
   on<_T extends keyof T>(key: _T, callback: HandlerCallback<T>): void;
   to<_T extends keyof T>(key: _T, callback: T[_T]): void;
 }