diff --git a/constance/admin.py b/constance/admin.py
index 3b8f9fe..d38d6ba 100644
--- a/constance/admin.py
+++ b/constance/admin.py
@@ -47,7 +47,10 @@ FIELDS = {
 
 def parse_additional_fields(fields):
     for key in fields:
-        field = fields[key]
+        field = list(fields[key])
+
+        if len(field) == 1:
+            field.append({})
 
         field[0] = import_string(field[0])
 
@@ -58,6 +61,8 @@ def parse_additional_fields(fields):
             if 'widget_kwargs' in field[1]:
                 del field[1]['widget_kwargs']
 
+        fields[key] = field
+
     return fields
 
 
diff --git a/tests/settings.py b/tests/settings.py
index 361a1b9..1f2e2f6 100644
--- a/tests/settings.py
+++ b/tests/settings.py
@@ -57,7 +57,9 @@ CONSTANCE_ADDITIONAL_FIELDS = {
          'widget': 'django.forms.Select',
          'choices': (("-----", None), ("yes", "Yes"), ("no", "No"))
          }],
-     }
+     # note this intentionally uses a tuple so that we can test immutable
+     'email': ('django.forms.fields.EmailField',),
+}
 
 CONSTANCE_CONFIG = {
     'INT_VALUE': (1, 'some int'),
@@ -73,6 +75,7 @@ CONSTANCE_CONFIG = {
     'TIME_VALUE': (time(23, 59, 59), 'And happy New Year'),
     'CHOICE_VALUE': ('yes', 'select yes or no', 'yes_no_null_select'),
     'LINEBREAK_VALUE': ('Spam spam', 'eggs\neggs'),
+    'EMAIL_VALUE': ('test@example.com', 'An email', 'email'),
 }
 
 DEBUG = True
diff --git a/tests/storage.py b/tests/storage.py
index 338daae..36cdbde 100644
--- a/tests/storage.py
+++ b/tests/storage.py
@@ -28,6 +28,8 @@ class StorageTestsMixin(object):
         self.assertEqual(self.config.DATE_VALUE, date(2010, 12, 24))
         self.assertEqual(self.config.TIME_VALUE, time(23, 59, 59))
         self.assertEqual(self.config.CHOICE_VALUE, 'yes')
+        self.assertEqual(self.config.EMAIL_VALUE, 'test@example.com')
+
 
         # set values
         self.config.INT_VALUE = 100
@@ -41,6 +43,7 @@ class StorageTestsMixin(object):
         self.config.DATE_VALUE = date(2001, 12, 20)
         self.config.TIME_VALUE = time(1, 59, 0)
         self.config.CHOICE_VALUE = 'no'
+        self.config.EMAIL_VALUE = 'foo@bar.com'
 
         # read again
         self.assertEqual(self.config.INT_VALUE, 100)
@@ -54,6 +57,8 @@ class StorageTestsMixin(object):
         self.assertEqual(self.config.DATE_VALUE, date(2001, 12, 20))
         self.assertEqual(self.config.TIME_VALUE, time(1, 59, 0))
         self.assertEqual(self.config.CHOICE_VALUE, 'no')
+        self.assertEqual(self.config.EMAIL_VALUE, 'foo@bar.com')
+
 
     def test_nonexistent(self):
         try: