diff --git a/src/types.ts b/src/types.ts
index 2420635..ee58fa3 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -25,11 +25,15 @@ type BaseSelector<F extends (...args: any) => any, STATE> = (
     state: STATE,
 ) => ReturnType<F>;
 
-type BaseSelectors<S, STATE> = {
+type BaseSelectors<S extends Record<string, any>, STATE> = {
     [key in keyof S]: BaseSelector<S[key], STATE>;
 };
 
-export type AggregateSelectors<S, SUBS, STATE = {}> = BaseSelectors<
+export type AggregateSelectors<
+    S extends Record<string, (...args: any) => any>,
+    SUBS extends Record<string, Dux>,
+    STATE = {},
+> = BaseSelectors<
     UnionToIntersection<SelectorsOf<SUBS[keyof SUBS]> | S>,
     STATE
 >;