diff --git a/types/spected/index.d.ts b/types/spected/index.d.ts
index 7757a05aed..691abd0355 100644
--- a/types/spected/index.d.ts
+++ b/types/spected/index.d.ts
@@ -4,7 +4,7 @@
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.8
 
-declare function spected<ROOTINPUT, SPEC = SpecObject<ROOTINPUT, ROOTINPUT>>(spec: SPEC, input: ROOTINPUT): Result<ROOTINPUT, SPEC>;
+declare function spected<ROOTINPUT, SPEC extends SpecValue<ROOTINPUT, ROOTINPUT> = SpecValue<ROOTINPUT, ROOTINPUT>>(spec: SPEC, input: ROOTINPUT): Result<ROOTINPUT, SPEC>;
 
 type Predicate<INPUT, ROOTINPUT> = (value: INPUT, inputs: ROOTINPUT) => boolean;
 
@@ -12,20 +12,23 @@ type ErrorMsg<INPUT> =
     | (string | number | boolean | symbol | null | undefined | object)
     | ((value: INPUT, field: string) => any);
 
-type SpecArrayElement<INPUT, ROOTINPUT> = [Predicate<INPUT, ROOTINPUT>, ErrorMsg<INPUT>];
+export type Spec<INPUT, ROOTINPUT = any> = [Predicate<INPUT, ROOTINPUT>, ErrorMsg<INPUT>];
 
-export type SpecArray<INPUT, ROOTINPUT> = ReadonlyArray<SpecArrayElement<INPUT, ROOTINPUT>>;
+export type SpecArray<INPUT, ROOTINPUT = any> = Array<Spec<INPUT, ROOTINPUT>>;
 
-export type SpecFunction<INPUT, ROOTINPUT> = INPUT extends ReadonlyArray<infer U>
+export type SpecFunction<INPUT, ROOTINPUT = any> = [INPUT] extends [ReadonlyArray<infer U>]
     ? (value: INPUT) => ReadonlyArray<SpecArray<U, ROOTINPUT>>
-    : (value: INPUT) => SpecObject<INPUT, ROOTINPUT>;
+    : [INPUT] extends [object]
+        ? (value: INPUT) => SpecObject<INPUT, ROOTINPUT>
+        : (value: INPUT) => SpecArray<INPUT, ROOTINPUT>;
 
-export type SpecObject<INPUT, ROOTINPUT> = Partial<{[key in keyof INPUT]: SpecValue<INPUT[key], ROOTINPUT>}>;
+export type SpecObject<INPUT, ROOTINPUT = any> = Partial<{[key in keyof INPUT]: SpecValue<INPUT[key], ROOTINPUT>}>;
 
-export type SpecValue<INPUT, ROOTINPUT> =
-    | SpecArray<INPUT, ROOTINPUT>
-    | SpecFunction<INPUT, ROOTINPUT>
-    | SpecObject<INPUT, ROOTINPUT>;
+export type SpecValue<INPUT, ROOTINPUT = any> = [INPUT] extends [ReadonlyArray<any>]
+    ? SpecArray<INPUT, ROOTINPUT> | SpecFunction<INPUT, ROOTINPUT>
+        : [INPUT] extends [object]
+            ? SpecArray<INPUT, ROOTINPUT> | SpecFunction<INPUT, ROOTINPUT> | SpecObject<INPUT, ROOTINPUT>
+            : SpecArray<INPUT, ROOTINPUT> | SpecFunction<INPUT, ROOTINPUT>;
 
 export type Result<INPUT, SPEC> = {[key in keyof INPUT]: true | any[] | Result<INPUT[key], any>};