diff --git a/website/announcements/tests.py b/website/announcements/tests.py
new file mode 100644
index 0000000000000000000000000000000000000000..db46de0902eca4394f026b621bccfe85eeb56589
--- /dev/null
+++ b/website/announcements/tests.py
@@ -0,0 +1,88 @@
+from django.contrib.auth.models import AnonymousUser, User
+from django.contrib.sessions.middleware import SessionMiddleware
+from django.test import TestCase, RequestFactory
+from django.urls import reverse
+
+from announcements.views import close_announcement
+
+
+class AnnouncementCloseTestCase(TestCase):
+
+    def setUp(self):
+        self.factory = RequestFactory()
+        self.user = User.objects.create_user(
+            username='thom',
+            email='test@example.com',
+            password='top secret',
+        )
+        self.middleware = SessionMiddleware()
+
+    def test_get_request(self):
+        for user in [self.user, AnonymousUser()]:
+            request = self.factory.get(
+                reverse('announcements:close-announcement'))
+            self.middleware.process_request(request)
+            with self.subTest(user=user):
+                request.user = user
+                response = close_announcement(request)
+                self.assertEqual(response.status_code, 405)
+
+    def test_post_no_id(self):
+        request = self.factory.post(
+            reverse('announcements:close-announcement'))
+        self.middleware.process_request(request)
+        request.user = AnonymousUser()
+        response = close_announcement(request)
+        self.assertEqual(response.status_code, 400)
+
+    def test_post_id_string(self):
+        request = self.factory.post(
+            reverse('announcements:close-announcement'),
+            {'id': 'bla'})
+        self.middleware.process_request(request)
+        request.user = AnonymousUser()
+        response = close_announcement(request)
+        self.assertEqual(response.status_code, 400)
+
+    def test_valid_request_anonymous(self):
+        request = self.factory.post(
+            reverse('announcements:close-announcement'),
+            {'id': 3})
+        self.middleware.process_request(request)
+        request.user = AnonymousUser()
+        response = close_announcement(request)
+
+        self.assertEqual(response.status_code, 204)
+        self.assertIn('closed_announcements', request.session)
+        self.assertIn(3, request.session['closed_announcements'])
+        self.assertTrue(request.session.modified)
+        self.assertEqual(response.content, b'')
+
+    def test_valid_request_logged_in(self):
+        request = self.factory.post(
+            reverse('announcements:close-announcement'),
+            {'id': 3})
+        self.middleware.process_request(request)
+        request.user = self.user
+        response = close_announcement(request)
+
+        self.assertEqual(response.status_code, 204)
+        self.assertIn('closed_announcements', request.session)
+        self.assertIn(3, request.session['closed_announcements'])
+        self.assertEqual(response.content, b'')
+
+    def test_valid_alread_canceled(self):
+        request = self.factory.post(
+            reverse('announcements:close-announcement'),
+            {'id': 3})
+        self.middleware.process_request(request)
+        request.session['closed_announcements'] = [3]
+        request.user = AnonymousUser()
+        response = close_announcement(request)
+
+        self.assertEqual(response.status_code, 204)
+        self.assertIn('closed_announcements', request.session)
+        self.assertIn(3, request.session['closed_announcements'])
+        self.assertEqual(len(request.session['closed_announcements']), 1)
+        self.assertTrue(request.session.modified)
+        self.assertEqual(response.content, b'')
diff --git a/website/announcements/views.py b/website/announcements/views.py
index 6ab4d85ed20f584012b030b627e8f7cf7b137ead..d23b7f8e05b1679576d4fff069ae72b19f760387 100644
--- a/website/announcements/views.py
+++ b/website/announcements/views.py
@@ -12,7 +12,11 @@ def close_announcement(request):
     """
     if 'id' not in request.POST:
         return HttpResponseBadRequest("no id specified")
-    announcement_id = int(request.POST['id'])
+    try:
+        announcement_id = int(request.POST['id'])
+    except ValueError:
+        return HttpResponseBadRequest("no integer id specified")
+
     # if we do not have a list of closed announcements yet:
     if 'closed_announcements' not in request.session:
         request.session['closed_announcements'] = []  # cannot use sets here :(