diff --git a/src/AuthenticatableInterface.php b/src/AuthenticatableInterface.php
index cd918a7..8eae47a 100644
--- a/src/AuthenticatableInterface.php
+++ b/src/AuthenticatableInterface.php
@@ -6,6 +6,6 @@
 
 interface AuthenticatableInterface
 {
-    public function getAuthIdentifier(): mixed;
+    public function getAuthIdentifier();
     public function getAuthPassword(): string;
 }
\ No newline at end of file
diff --git a/src/Guard/GuardHelper.php b/src/Guard/GuardHelper.php
index 8b41517..2fedf01 100644
--- a/src/Guard/GuardHelper.php
+++ b/src/Guard/GuardHelper.php
@@ -22,7 +22,7 @@ trait GuardHelper
     /**
      * @return mixed
      */
-    public function id(): mixed
+    public function id()
     {
         if ($this->user()) {
             return $this->user()->getAuthIdentifier();