diff --git a/django/contrib/flatpages/forms.py b/django/contrib/flatpages/forms.py
index 24a6e7b58e..8ffae833e5 100644
--- a/django/contrib/flatpages/forms.py
+++ b/django/contrib/flatpages/forms.py
@@ -1,6 +1,7 @@
 from django import forms
-from django.utils.translation import ugettext_lazy as _
+from django.conf import settings
 from django.contrib.flatpages.models import FlatPage
+from django.utils.translation import ugettext, ugettext_lazy as _
 
 class FlatpageForm(forms.ModelForm):
     url = forms.RegexField(label=_("URL"), max_length=100, regex=r'^[-\w/\.~]+$',
@@ -12,6 +13,16 @@ class FlatpageForm(forms.ModelForm):
     class Meta:
         model = FlatPage
 
+    def clean_url(self):
+        url = self.cleaned_data['url']
+        if not url.startswith('/'):
+            raise forms.ValidationError(ugettext("URL is missing a leading slash."))
+        if (settings.APPEND_SLASH and
+            'django.middleware.common.CommonMiddleware' in settings.MIDDLEWARE_CLASSES and
+            not url.endswith('/')):
+            raise forms.ValidationError(ugettext("URL is missing a trailing slash."))
+        return url
+
     def clean(self):
         url = self.cleaned_data.get('url', None)
         sites = self.cleaned_data.get('sites', None)
diff --git a/django/contrib/flatpages/tests/forms.py b/django/contrib/flatpages/tests/forms.py
index 7f617d52a5..884c40acc8 100644
--- a/django/contrib/flatpages/tests/forms.py
+++ b/django/contrib/flatpages/tests/forms.py
@@ -2,6 +2,8 @@ from django.conf import settings
 from django.contrib.flatpages.forms import FlatpageForm
 from django.contrib.flatpages.models import FlatPage
 from django.test import TestCase
+from django.test.utils import override_settings
+from django.utils import translation
 
 class FlatpageAdminFormTests(TestCase):
     def setUp(self):
@@ -23,9 +25,29 @@ class FlatpageAdminFormTests(TestCase):
         self.assertFalse(FlatpageForm(data=dict(url='/a & char/', **self.form_data)).is_valid())
         self.assertFalse(FlatpageForm(data=dict(url='/a ? char/', **self.form_data)).is_valid())
 
+    def test_flatpage_requires_leading_slash(self):
+        form = FlatpageForm(data=dict(url='no_leading_slash/', **self.form_data))
+        with translation.override('en'):
+            self.assertFalse(form.is_valid())
+            self.assertEqual(form.errors['url'], ["URL is missing a leading slash."])
+
+    @override_settings(APPEND_SLASH=True,
+            MIDDLEWARE_CLASSES=('django.middleware.common.CommonMiddleware',))
+    def test_flatpage_requires_trailing_slash_with_append_slash(self):
+        form = FlatpageForm(data=dict(url='/no_trailing_slash', **self.form_data))
+        with translation.override('en'):
+            self.assertFalse(form.is_valid())
+            self.assertEqual(form.errors['url'], ["URL is missing a trailing slash."])
+
+    @override_settings(APPEND_SLASH=False,
+            MIDDLEWARE_CLASSES=('django.middleware.common.CommonMiddleware',))
+    def test_flatpage_doesnt_requires_trailing_slash_without_append_slash(self):
+        form = FlatpageForm(data=dict(url='/no_trailing_slash', **self.form_data))
+        self.assertTrue(form.is_valid())
+
     def test_flatpage_admin_form_url_uniqueness_validation(self):
         "The flatpage admin form correctly enforces url uniqueness among flatpages of the same site"
-        data = dict(url='/myflatpage1', **self.form_data)
+        data = dict(url='/myflatpage1/', **self.form_data)
 
         FlatpageForm(data=data).save()
 
@@ -35,7 +57,7 @@ class FlatpageAdminFormTests(TestCase):
 
         self.assertEqual(
             f.errors,
-            {'__all__': [u'Flatpage with url /myflatpage1 already exists for site example.com']})
+            {'__all__': [u'Flatpage with url /myflatpage1/ already exists for site example.com']})
 
     def test_flatpage_admin_form_edit(self):
         """
@@ -44,10 +66,10 @@ class FlatpageAdminFormTests(TestCase):
 
         """
         existing = FlatPage.objects.create(
-            url="/myflatpage1", title="Some page", content="The content")
+            url="/myflatpage1/", title="Some page", content="The content")
         existing.sites.add(settings.SITE_ID)
 
-        data = dict(url='/myflatpage1', **self.form_data)
+        data = dict(url='/myflatpage1/', **self.form_data)
 
         f = FlatpageForm(data=data, instance=existing)