diff --git a/attr/validators.py b/attr/validators.py
index 79969beb..01b7b108 100644
--- a/attr/validators.py
+++ b/attr/validators.py
@@ -106,9 +106,9 @@ class _OptionalValidator(object):
 def optional(validator):
     """
     A validator that makes an attribute optional.  An optional attribute is one
-    which can be set to None in addition to satisfying the requirements of the
-    sub-validator.
+    which can be set to ``None`` in addition to satisfying the requirements of
+    the sub-validator.
 
-    :param validator: Any other validator you wish to make optional.
+    :param validator: A validator that is used for non-``None`` values.
     """
     return _OptionalValidator(validator)
diff --git a/tests/test_validators.py b/tests/test_validators.py
index dbd3cb1e..7be59b60 100644
--- a/tests/test_validators.py
+++ b/tests/test_validators.py
@@ -128,13 +128,6 @@ class TestOptional(object):
         v = optional(instance_of(int))
         v(None, simple_attr("test"), None)
 
-    def test_subclass(self):
-        """
-        Subclasses are accepted too.
-        """
-        v = optional(instance_of(int))
-        v(None, simple_attr("test"), True)
-
     def test_fail(self):
         """
         Raises `TypeError` on wrong types.