diff --git a/configurations/utils.py b/configurations/utils.py
index f864b48..ce5e598 100644
--- a/configurations/utils.py
+++ b/configurations/utils.py
@@ -1,3 +1,4 @@
+import inspect
 import sys
 
 from django.core.exceptions import ImproperlyConfigured
@@ -122,3 +123,76 @@ except ImportError:
                         raise Exception
                 except:  # Needed because we might need to catch a SystemExit
                     largs.append(arg)
+
+
+# Copied over from Sphinx
+if sys.version_info >= (3, 0):
+    from functools import partial
+
+    def getargspec(func):
+        """Like inspect.getargspec but supports functools.partial as well."""
+        if inspect.ismethod(func):
+            func = func.__func__
+        if type(func) is partial:
+            orig_func = func.func
+            argspec = getargspec(orig_func)
+            args = list(argspec[0])
+            defaults = list(argspec[3] or ())
+            kwoargs = list(argspec[4])
+            kwodefs = dict(argspec[5] or {})
+            if func.args:
+                args = args[len(func.args):]
+            for arg in func.keywords or ():
+                try:
+                    i = args.index(arg) - len(args)
+                    del args[i]
+                    try:
+                        del defaults[i]
+                    except IndexError:
+                        pass
+                except ValueError:   # must be a kwonly arg
+                    i = kwoargs.index(arg)
+                    del kwoargs[i]
+                    del kwodefs[arg]
+            return inspect.FullArgSpec(args, argspec[1], argspec[2],
+                                       tuple(defaults), kwoargs,
+                                       kwodefs, argspec[6])
+        while hasattr(func, '__wrapped__'):
+            func = func.__wrapped__
+        if not inspect.isfunction(func):
+            raise TypeError('%r is not a Python function' % func)
+        return inspect.getfullargspec(func)
+
+else:  # 2.6, 2.7
+    from functools import partial
+
+    def getargspec(func):
+        """Like inspect.getargspec but supports functools.partial as well."""
+        if inspect.ismethod(func):
+            func = func.im_func
+        parts = 0, ()
+        if type(func) is partial:
+            keywords = func.keywords
+            if keywords is None:
+                keywords = {}
+            parts = len(func.args), keywords.keys()
+            func = func.func
+        if not inspect.isfunction(func):
+            raise TypeError('%r is not a Python function' % func)
+        args, varargs, varkw = inspect.getargs(func.func_code)
+        func_defaults = func.func_defaults
+        if func_defaults is None:
+            func_defaults = []
+        else:
+            func_defaults = list(func_defaults)
+        if parts[0]:
+            args = args[parts[0]:]
+        if parts[1]:
+            for arg in parts[1]:
+                i = args.index(arg) - len(args)
+                del args[i]
+                try:
+                    del func_defaults[i]
+                except IndexError:
+                    pass
+        return inspect.ArgSpec(args, varargs, varkw, func_defaults)
diff --git a/configurations/values.py b/configurations/values.py
index 1b2b1c7..35287eb 100644
--- a/configurations/values.py
+++ b/configurations/values.py
@@ -8,7 +8,7 @@ from django.core import validators
 from django.core.exceptions import ValidationError, ImproperlyConfigured
 from django.utils import six
 
-from .utils import import_by_path
+from .utils import import_by_path, getargspec
 
 
 def setup_value(target, name, value):
@@ -140,10 +140,20 @@ class CastingMixin(object):
             error = 'Cannot use caster of {0} ({1!r})'.format(self,
                                                               self.caster)
             raise ValueError(error)
+        try:
+            arg_names = getargspec(self._caster)[0]
+            self._params = dict((name, kwargs[name])
+                                for name in arg_names
+                                if name in kwargs)
+        except TypeError:
+            self._params = {}
 
     def to_python(self, value):
         try:
-            return self._caster(value)
+            if self._params:
+                return self._caster(value, **self._params)
+            else:
+                return self._caster(value)
         except self.exception:
             raise ValueError(self.message.format(value))
 
diff --git a/tests/test_values.py b/tests/test_values.py
index 5d94fe1..83ded5d 100644
--- a/tests/test_values.py
+++ b/tests/test_values.py
@@ -295,6 +295,21 @@ class ValueTests(TestCase):
                     'USER': '',
                 }})
 
+    def test_database_url_additional_args(self):
+
+        def mock_database_url_caster(self, url, engine=None):
+            return { 'URL': url, 'ENGINE': engine }
+
+        with patch('configurations.values.DatabaseURLValue.caster', mock_database_url_caster):
+            value = DatabaseURLValue(engine='django_mysqlpool.backends.mysqlpool')
+            with env(DATABASE_URL='sqlite://'):
+                self.assertEqual(value.setup('DATABASE_URL'), {
+                    'default': {
+                        'URL': 'sqlite://',
+                        'ENGINE': 'django_mysqlpool.backends.mysqlpool'
+                    }
+                })
+
     def test_email_url_value(self):
         value = EmailURLValue()
         self.assertEqual(value.default, {})