diff --git a/doc/source/changelog.rst b/doc/source/changelog.rst
index 7805b68..d9218f6 100644
--- a/doc/source/changelog.rst
+++ b/doc/source/changelog.rst
@@ -2,6 +2,20 @@
 Change Log
 ==========
 
+v1.5.0
+======
+
+There is one minimally impactful breaking change in the 1.5.0 release:
+
+* Symmetric properties that are None will not map back to the enumeration value
+  by default. To replicate the previous behavior, pass True as the `match_none`
+  argument when instantiating the property with s().
+
+The 1.5.0 release includes two feature improvements:
+
+* Implemented `Configurable behavior for matching none on symmetric fields <https://github.com/bckohan/enum-properties/issues/44>`_
+
+
 v1.4.0
 ======
 
diff --git a/doc/source/usage.rst b/doc/source/usage.rst
index 400af38..18ee807 100644
--- a/doc/source/usage.rst
+++ b/doc/source/usage.rst
@@ -76,8 +76,10 @@ property symmetry. To mark a property as symmetric, use
     Color.RED == Color((1, 0, 0)) == Color('0xFF0000') == Color('0xff0000')
 
 Symmetric string properties are by default case sensitive. To mark a property
-as case insensitive, use the `case_fold=True` parameter on the
-:py:meth:`~enum_properties.s` value.
+as case insensitive, use the ``case_fold=True`` parameter on the
+:py:meth:`~enum_properties.s` value. By default, none values for symmetric
+properties will not be symmetric. To change this behavior pass:
+``match_none=True`` to :py:meth:`~enum_properties.s`.
 
 Symmetric property support is added through the
 :py:class:`~enum_properties.SymmetricMixin` class which is included in the
diff --git a/enum_properties/__init__.py b/enum_properties/__init__.py
index 33f0e4d..190b462 100644
--- a/enum_properties/__init__.py
+++ b/enum_properties/__init__.py
@@ -31,7 +31,7 @@
     cached_property = property  # pylint: disable=C0103
 
 
-VERSION = (1, 4, 0)
+VERSION = (1, 5, 0)
 
 __title__ = 'Enum Properties'
 __version__ = '.'.join(str(i) for i in VERSION)
@@ -77,7 +77,8 @@ class _SProp(_Prop):
 
 def s(  # pylint: disable=C0103
     prop_name,
-    case_fold=False
+    case_fold=False,
+    match_none=False
 ):
     """
     Add a symmetric property. Enumeration values will be coercible from this
@@ -86,12 +87,15 @@ def s(  # pylint: disable=C0103
     :param prop_name: The name of the property
     :param case_fold: If False, symmetric lookup will be
         case sensitive (default)
+    :param match_none: If True, none values will be symmetric, if False
+        (default), none values for symmetric properties will not map back to
+        the enumeration value.
     :return: a named symmetric property class
     """
     return type(
         prop_name,
         (_SProp,),
-        {'symmetric': True, 'case_fold': case_fold}
+        {'symmetric': True, 'case_fold': case_fold, 'match_none': match_none}
     )
 
 
@@ -447,6 +451,8 @@ def __new__(  # pylint: disable=W0221
                 )
 
         def add_sym_lookup(prop, p_val, enum_inst):
+            if p_val is None and not prop.match_none:
+                return
             if not isinstance(p_val, Hashable):
                 raise ValueError(
                     f'{cls}.{prop}:{p_val} is not hashable. Symmetrical '
diff --git a/enum_properties/tests/tests.py b/enum_properties/tests/tests.py
index f998156..84df359 100644
--- a/enum_properties/tests/tests.py
+++ b/enum_properties/tests/tests.py
@@ -259,6 +259,72 @@ class Color(
                 GREEN = 2, 'Verde', (0, 1, 0), '00ff00'
                 BLUE = 3, 'Azul', (0, 0, 1), '0000ff'
 
+    def test_symmetric_match_none_parameter(self):
+
+        # test default behavior
+        class ColorDefault(
+            EnumProperties,
+            p('spanish'),
+            s('rgb'),
+            s('hex')
+        ):
+
+            RED = 1, 'Roja', (1, 0, 0), 'ff0000'
+            GREEN = 2, 'Verde', (0, 1, 0), None
+            BLUE = 3, 'Azul', (0, 0, 1), None
+
+        self.assertEqual(ColorDefault.RED, 'ff0000')
+        self.assertNotEqual(ColorDefault.GREEN, None)
+        self.assertNotEqual(ColorDefault.BLUE, None)
+        self.assertRaises(ValueError, ColorDefault, None)
+        self.assertRaises(ValueError, ColorDefault, 'FF0000')
+        self.assertEqual(ColorDefault('ff0000'), ColorDefault.RED)
+        self.assertEqual(ColorDefault((1, 0, 0)), ColorDefault.RED)
+        self.assertEqual(ColorDefault((0, 1, 0)), ColorDefault.GREEN)
+        self.assertEqual(ColorDefault((0, 0, 1)), ColorDefault.BLUE)
+
+        class ColorNoMatchNone(
+            EnumProperties,
+            p('spanish'),
+            s('rgb'),
+            s('hex', case_fold=True, match_none=False)
+        ):
+
+            RED = 1, 'Roja', (1, 0, 0), 'ff0000'
+            GREEN = 2, 'Verde', (0, 1, 0), None
+            BLUE = 3, 'Azul', (0, 0, 1), None
+
+        self.assertEqual(ColorNoMatchNone.RED, 'fF0000')
+        self.assertNotEqual(ColorNoMatchNone.GREEN, None)
+        self.assertNotEqual(ColorNoMatchNone.BLUE, None)
+        self.assertRaises(ValueError, ColorNoMatchNone, None)
+        self.assertEqual(ColorNoMatchNone('Ff0000'), ColorNoMatchNone.RED)
+        self.assertEqual(ColorNoMatchNone((1, 0, 0)), ColorNoMatchNone.RED)
+        self.assertEqual(ColorNoMatchNone((0, 1, 0)), ColorNoMatchNone.GREEN)
+        self.assertEqual(ColorNoMatchNone((0, 0, 1)), ColorNoMatchNone.BLUE)
+
+        class ColorMatchNone(
+            EnumProperties,
+            p('spanish'),
+            s('rgb'),
+            s('hex', match_none=True)
+        ):
+
+            RED = 1, 'Roja', (1, 0, 0), 'ff0000'
+            GREEN = 2, 'Verde', (0, 1, 0), None
+            BLUE = 3, 'Azul', (0, 0, 1), None
+
+        self.assertNotEqual(ColorMatchNone.RED, 'FF0000')
+        self.assertEqual(ColorMatchNone.RED, 'ff0000')
+        self.assertEqual(ColorMatchNone.GREEN, None)
+        self.assertNotEqual(ColorMatchNone.BLUE, None)
+        self.assertEqual(ColorMatchNone(None), ColorMatchNone.GREEN)
+        self.assertEqual(ColorMatchNone('ff0000'), ColorMatchNone.RED)
+        self.assertRaises(ValueError, ColorMatchNone, 'FF0000')
+        self.assertEqual(ColorMatchNone((1, 0, 0)), ColorMatchNone.RED)
+        self.assertEqual(ColorMatchNone((0, 1, 0)), ColorMatchNone.GREEN)
+        self.assertEqual(ColorMatchNone((0, 0, 1)), ColorMatchNone.BLUE)
+
     def test_properties_no_symmetry(self):
         """
         Tests that absence of SymmetricMixin works but w/o symmetric
@@ -546,7 +612,7 @@ class Color(
             EnumProperties,
             p('spanish'),
             s('rgb'),
-            s('hex', case_fold=True)
+            s('hex', case_fold=True, match_none=True)
         ):
             RED = 1, 'Roja', (1, 0, 0), 'ff0000'
             GREEN = 2, None, (0, 1, 0), '00ff00'
@@ -1676,6 +1742,26 @@ class Type3:
         self.assertTrue(MyEnum.Type3.value().__class__ is MyEnum.Type3.value)
 
 
+class TestGiantFlags(TestCase):
+
+    def test_over64_flags(self):
+
+        class BigFlags(IntFlagProperties, p('label')):
+
+            ONE = 2**0, 'one'
+            MIDDLE = 2**64, 'middle'
+            MIXED = ONE | MIDDLE, 'mixed'
+            LAST = 2**128, 'last'
+
+        self.assertEqual((BigFlags.ONE | BigFlags.LAST).value, 2**128 + 1)
+        self.assertEqual(
+            (BigFlags.MIDDLE | BigFlags.LAST).value, 2**128 + 2**64
+        )
+        self.assertEqual(
+            (BigFlags.MIDDLE | BigFlags.ONE).label, 'mixed'
+        )
+
+
 class TestSpecialize(TestCase):
     """
     Test the specialize decorator
@@ -1872,3 +1958,22 @@ def test_property_access_time(self):
 
         for_loop_time = perf_counter() - for_loop_time
         print('for loop time: {}'.format(for_loop_time))
+
+    def test_symmetric_mapping(self):
+        """
+        Symmetric mapping benchmarks
+
+        v1.4.0 ISOCountry: ~3 seconds (macbook M1 Pro)
+        v1.4.1 ISOCountry: ~ seconds (macbook M1 Pro) (x faster)
+        """
+        self.assertEqual(
+            self.ISOCountry(self.ISOCountry.US.full_name.lower()),
+            self.ISOCountry.US
+        )
+        from time import perf_counter
+        for_loop_time = perf_counter()
+        for i in range(1000000):
+            self.ISOCountry(self.ISOCountry.US.full_name.lower())
+
+        for_loop_time = perf_counter() - for_loop_time
+        print('for loop time: {}'.format(for_loop_time))
diff --git a/pyproject.toml b/pyproject.toml
index d2beb2f..4748eff 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "enum-properties"
-version = "1.4.0"
+version = "1.5.0"
 description = "Add properties and method specializations to Python enumeration values with a simple declarative syntax."
 authors = ["Brian Kohan <bckohan@gmail.com>"]
 license = "MIT"