diff --git a/src/pretix/base/models/event.py b/src/pretix/base/models/event.py
index b60546123a..5925488470 100644
--- a/src/pretix/base/models/event.py
+++ b/src/pretix/base/models/event.py
@@ -15,6 +15,7 @@ from pretix.base.email import CustomSMTPBackend
 from pretix.base.i18n import I18nCharField
 from pretix.base.models.base import LoggedModel
 from pretix.base.settings import SettingsProxy
+from pretix.base.validators import EventSlugBlacklistValidator
 
 from .auth import User
 from .organizer import Organizer
@@ -65,7 +66,8 @@ class Event(LoggedModel):
             RegexValidator(
                 regex="^[a-zA-Z0-9.-]+$",
                 message=_("The slug may only contain letters, numbers, dots and dashes."),
-            )
+            ),
+            EventSlugBlacklistValidator()
         ],
         verbose_name=_("Slug"),
     )
diff --git a/src/pretix/base/models/organizer.py b/src/pretix/base/models/organizer.py
index 93cce5e536..baf6fb915c 100644
--- a/src/pretix/base/models/organizer.py
+++ b/src/pretix/base/models/organizer.py
@@ -5,6 +5,7 @@ from django.utils.translation import ugettext_lazy as _
 
 from pretix.base.models.base import LoggedModel
 from pretix.base.settings import SettingsProxy
+from pretix.base.validators import OrganizerSlugBlacklistValidator
 
 from .auth import User
 from .settings import OrganizerSetting
@@ -34,7 +35,8 @@ class Organizer(LoggedModel):
             RegexValidator(
                 regex="^[a-zA-Z0-9.-]+$",
                 message=_("The slug may only contain letters, numbers, dots and dashes.")
-            )
+            ),
+            OrganizerSlugBlacklistValidator()
         ],
         verbose_name=_("Slug"),
     )
diff --git a/src/pretix/base/validators.py b/src/pretix/base/validators.py
new file mode 100644
index 0000000000..4f5688cc78
--- /dev/null
+++ b/src/pretix/base/validators.py
@@ -0,0 +1,48 @@
+from django.core.exceptions import ValidationError
+from django.utils.translation import ugettext_lazy as _
+
+
+class BlacklistValidator:
+
+    blacklist = []
+
+    def __call__(self, value):
+        # Validation logic
+        if value in self.blacklist:
+            raise ValidationError(
+                _('This slug has an invalid value: %(value)s.'),
+                code='invalid',
+                params={'value': value},
+            )
+
+
+class EventSlugBlacklistValidator(BlacklistValidator):
+
+    blacklist = [
+        'download',
+        'healthcheck',
+        'locale',
+        'control',
+        'redirect',
+        'jsi18n',
+        'metrics',
+        '_global',
+        '__debug__'
+    ]
+
+
+class OrganizerSlugBlacklistValidator(BlacklistValidator):
+
+    blacklist = [
+        'download',
+        'healthcheck',
+        'locale',
+        'control',
+        'pretixdroid',
+        'redirect',
+        'jsi18n',
+        'metrics',
+        '_global',
+        '__debug__',
+        'about'
+    ]
diff --git a/src/tests/base/test_models.py b/src/tests/base/test_models.py
index 172398eec0..ad79d44f0a 100644
--- a/src/tests/base/test_models.py
+++ b/src/tests/base/test_models.py
@@ -1,3 +1,4 @@
+import datetime
 import sys
 from datetime import timedelta
 
@@ -601,6 +602,16 @@ class EventTest(TestCase):
 
         self.assertIn('presale_end', str(context.exception))
 
+    def test_slug_validation(self):
+        event = Event(
+            organizer=self.organizer, name='Download', slug='download',
+            date_from=datetime.datetime(2013, 12, 26, tzinfo=datetime.timezone.utc)
+        )
+        with self.assertRaises(ValidationError) as context:
+            event.full_clean()
+
+        self.assertIn('slug', str(context.exception))
+
 
 class CachedFileTestCase(TestCase):
     def test_file_handling(self):
diff --git a/src/tests/presale/test_event.py b/src/tests/presale/test_event.py
index 40b33098a5..d7d1e309ba 100644
--- a/src/tests/presale/test_event.py
+++ b/src/tests/presale/test_event.py
@@ -2,6 +2,7 @@ import datetime
 from decimal import Decimal
 
 from django.core import mail
+from django.core.exceptions import ValidationError
 from django.test import TestCase
 from django.utils.timezone import now
 from tests.base import SoupTest
@@ -469,3 +470,19 @@ class TestResendLink(EventTestMixin, SoupTest):
         self.assertEqual(len(mail.outbox), 1)
         self.assertIn('DUMMY1', mail.outbox[0].body)
         self.assertIn('DUMMY2', mail.outbox[0].body)
+
+
+class EventSlugBlacklistValidatorTest(EventTestMixin, SoupTest):
+    def test_slug_validation(self):
+        event = Event(
+            organizer=self.orga,
+            name='download',
+            slug='download',
+            date_from=datetime.datetime(2013, 12, 26, tzinfo=datetime.timezone.utc),
+            live=True
+        )
+        with self.assertRaises(ValidationError):
+            if event.full_clean():
+                event.save()
+
+        self.assertEqual(Event.objects.filter(name='download').count(), 0)