diff --git a/src/index.ts b/src/index.ts
index 574e128..c0ff0c0 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -35,7 +35,7 @@ export * from './interface';
  */
 class Schema {
   // ========================= Static =========================
-  static register = function register(type: string, validator) {
+  static register = function register(type: string, validator: ExecuteValidator) {
     if (typeof validator !== 'function') {
       throw new Error(
         'Cannot register a validator by type, validator is not a function',