diff --git a/src/Valitron/Validator.php b/src/Valitron/Validator.php
index b92def2..94af820 100644
--- a/src/Valitron/Validator.php
+++ b/src/Valitron/Validator.php
@@ -489,7 +489,7 @@ class Validator
         if (!is_array($params[0])) {
             $params[0] = array($params[0]);
         }
-        if (is_scalar($value)) {
+        if (is_scalar($value) || is_null($value)) {
             return $this->validateIn($field, $value, $params);
         }
 
diff --git a/tests/Valitron/ValidateTest.php b/tests/Valitron/ValidateTest.php
index fc9f229..28cacfc 100644
--- a/tests/Valitron/ValidateTest.php
+++ b/tests/Valitron/ValidateTest.php
@@ -484,7 +484,7 @@ class ValidateTest extends BaseTestCase
         $v->rule('lengthMin', 'str', 4);
         $this->assertTrue($v->validate());
     }
-    
+
     public function testLengthMinValidAltSyntax()
     {
         $v = new Valitron\Validator(array('username' => 'martha'));
@@ -1720,6 +1720,15 @@ class ValidateTest extends BaseTestCase
         $this->assertFalse($v->validate());
     }
 
+    public function testSubsetAcceptNullValue()
+    {
+    		// rule value equals null
+        $v = new Validator(array('test_field' => null));
+        $v->rule('required', 'test_field');
+        $v->rule('subset', 'test_field', array('black', 45));
+        $this->assertFalse($v->validate());
+    }
+
     public function testContainsUniqueValid()
     {
         // numeric values