diff --git a/src/index.ts b/src/index.ts
index 8f9f9a6..49710cf 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,4 +1,4 @@
-type Parser<T> = (value: unknown) => T | null;
+type Parser<T> = (value: unknown) => Required<T> | null;
 
 function hasProperties<T extends object, K extends string>(obj: T, ...keys: K[]): obj is T & { [J in K]: unknown } {
     return !!obj && keys.every(key => obj.hasOwnProperty(key));