diff --git a/fernet_fields/__init__.py b/fernet_fields/__init__.py
index 0d009e0..739ee5c 100644
--- a/fernet_fields/__init__.py
+++ b/fernet_fields/__init__.py
@@ -1,3 +1,3 @@
 from .fields import *  # noqa
 
-__version__ = '0.5'
+__version__ = '0.5.1.4'
diff --git a/fernet_fields/fields.py b/fernet_fields/fields.py
index 025da38..ee5bc8a 100644
--- a/fernet_fields/fields.py
+++ b/fernet_fields/fields.py
@@ -1,8 +1,12 @@
-from cryptography.fernet import Fernet, MultiFernet
+import base64
+import os
+
+from cryptography.fernet import Fernet as OldFernet, MultiFernet
+from cryptography.hazmat.backends import default_backend
 from django.conf import settings
 from django.core.exceptions import FieldError, ImproperlyConfigured
 from django.db import models
-from django.utils.encoding import force_bytes, force_text
+from django.utils.encoding import force_bytes, force_str
 from django.utils.functional import cached_property
 
 from . import hkdf
@@ -16,9 +20,31 @@
     'EncryptedIntegerField',
     'EncryptedDateField',
     'EncryptedDateTimeField',
+    'StrongerFernet',
 ]
 
 
+class StrongerFernet(OldFernet):
+    # noinspection PyMissingConstructor
+    def __init__(self, key, backend=None):
+        if backend is None:
+            backend = default_backend()
+
+        key = base64.urlsafe_b64decode(key)
+        if len(key) != 48:
+            raise ValueError(
+                "Fernet key must be 48 url-safe base64-encoded bytes."
+            )
+
+        self._signing_key = key[:16]
+        self._encryption_key = key[16:]
+        self._backend = backend
+
+    @classmethod
+    def generate_key(cls):
+        return base64.urlsafe_b64encode(os.urandom(48))
+
+
 class EncryptedField(models.Field):
     """A field that encrypts values using Fernet symmetric encryption."""
     _internal_type = 'BinaryField'
@@ -39,6 +65,7 @@ def __init__(self, *args, **kwargs):
                 "%s does not support db_index=True."
                 % self.__class__.__name__
             )
+        self.allowed_unencrypted_values = kwargs.pop('allowed_unencrypted_values', [])
         super(EncryptedField, self).__init__(*args, **kwargs)
 
     @cached_property
@@ -57,8 +84,8 @@ def fernet_keys(self):
     @cached_property
     def fernet(self):
         if len(self.fernet_keys) == 1:
-            return Fernet(self.fernet_keys[0])
-        return MultiFernet([Fernet(k) for k in self.fernet_keys])
+            return StrongerFernet(self.fernet_keys[0])
+        return MultiFernet([StrongerFernet(k) for k in self.fernet_keys])
 
     def get_internal_type(self):
         return self._internal_type
@@ -71,10 +98,11 @@ def get_db_prep_save(self, value, connection):
             retval = self.fernet.encrypt(force_bytes(value))
             return connection.Database.Binary(retval)
 
-    def from_db_value(self, value, expression, connection, context):
+    def from_db_value(self, value, expression, connection, context=None):
         if value is not None:
-            value = bytes(value)
-            return self.to_python(force_text(self.fernet.decrypt(value)))
+            if value not in self.allowed_unencrypted_values:
+                value = self.fernet.decrypt(force_bytes(value))
+            return self.to_python(force_str(value))
 
     @cached_property
     def validators(self):
diff --git a/fernet_fields/hkdf.py b/fernet_fields/hkdf.py
index 5bb5baa..2147055 100644
--- a/fernet_fields/hkdf.py
+++ b/fernet_fields/hkdf.py
@@ -15,7 +15,7 @@ def derive_fernet_key(input_key):
     """Derive a 32-bit b64-encoded Fernet key from arbitrary input key."""
     hkdf = HKDF(
         algorithm=hashes.SHA256(),
-        length=32,
+        length=48,
         salt=salt,
         info=info,
         backend=backend,
diff --git a/fernet_fields/test/test_fields.py b/fernet_fields/test/test_fields.py
index bd8e5b8..f519fa6 100644
--- a/fernet_fields/test/test_fields.py
+++ b/fernet_fields/test/test_fields.py
@@ -1,4 +1,3 @@
-from cryptography.fernet import Fernet
 from datetime import date, datetime
 
 from django.core.exceptions import FieldError, ImproperlyConfigured
@@ -29,8 +28,8 @@ def test_key_rotation(self, settings):
         settings.FERNET_KEYS = ['key1', 'key2']
         f = fields.EncryptedTextField()
 
-        enc1 = Fernet(f.fernet_keys[0]).encrypt(b'enc1')
-        enc2 = Fernet(f.fernet_keys[1]).encrypt(b'enc2')
+        enc1 = fields.StrongerFernet(f.fernet_keys[0]).encrypt(b'enc1')
+        enc2 = fields.StrongerFernet(f.fernet_keys[1]).encrypt(b'enc2')
 
         assert f.fernet.decrypt(enc1) == b'enc1'
         assert f.fernet.decrypt(enc2) == b'enc2'
@@ -38,10 +37,10 @@ def test_key_rotation(self, settings):
     def test_no_hkdf(self, settings):
         """Can set FERNET_USE_HKDF=False to avoid HKDF."""
         settings.FERNET_USE_HKDF = False
-        k1 = Fernet.generate_key()
+        k1 = fields.StrongerFernet.generate_key()
         settings.FERNET_KEYS = [k1]
         f = fields.EncryptedTextField()
-        fernet = Fernet(k1)
+        fernet = fields.StrongerFernet(k1)
 
         assert fernet.decrypt(f.fernet.encrypt(b'foo')) == b'foo'
 
diff --git a/setup.py b/setup.py
index 82ea323..00cb20a 100644
--- a/setup.py
+++ b/setup.py
@@ -14,7 +14,7 @@ def get_version():
 
 
 setup(
-    name='django-fernet-fields',
+    name='singular-django-fernet-fields',
     version=get_version(),
     description="Fernet-encrypted model fields for Django",
     long_description=long_description,