diff --git a/src/EnumConcern.php b/src/EnumConcern.php
index 28f2bb1..a190a40 100755
--- a/src/EnumConcern.php
+++ b/src/EnumConcern.php
@@ -126,7 +126,7 @@ public static function hasName(string $name): bool
     /**
      * Compares two enum instances for equality.
      */
-    public function is(self $other): bool
+    public function is(UnitEnum $other): bool
     {
         return $this === $other;
     }
@@ -134,7 +134,7 @@ public function is(self $other): bool
     /**
      * Checks if two enum instances are not equal.
      */
-    public function isNot(self $other): bool
+    public function isNot(UnitEnum $other): bool
     {
         return !$this->is($other);
     }