diff --git a/src/interfaces/type.ts b/src/interfaces/type.ts
index 4c91d9b..9e6870d 100644
--- a/src/interfaces/type.ts
+++ b/src/interfaces/type.ts
@@ -66,10 +66,10 @@ export interface Signatures<T> {
    re:   (a: T) => RealType<T>
 }
 
-type SignatureKey = keyof Signatures<unknown>
+type SignatureKey<T> = keyof Signatures<T>
 
-export type Signature<Name extends SignatureKey, T> = Signatures<T>[Name]
-export type Returns<Name extends SignatureKey, T> = ReturnType<Signatures<T>[Name]>
-export type Dependencies<Name extends SignatureKey, T> = {[K in Name]: Signature<K, T>}
+export type Signature<Name extends SignatureKey<T>, T> = Signatures<T>[Name]
+export type Returns<Name extends SignatureKey<T>, T> = ReturnType<Signatures<T>[Name]>
+export type Dependencies<Name extends SignatureKey<T>, T> = {[K in Name]: Signature<K, T>}
 
 export type AliasOf<Name extends string, T> = T & {aliasOf?: Name}