diff --git a/wagtail/wagtailimages/tests/tests.py b/wagtail/wagtailimages/tests/tests.py
index 2d01989bc9..d414a66d20 100644
--- a/wagtail/wagtailimages/tests/tests.py
+++ b/wagtail/wagtailimages/tests/tests.py
@@ -17,7 +17,7 @@ from wagtail.wagtailimages.formats import Format, get_image_format, register_ima
 from wagtail.wagtailimages.forms import get_image_form
 from wagtail.wagtailimages.models import Image as WagtailImage
 from wagtail.wagtailimages.rect import Rect, Vector
-from wagtail.wagtailimages.views.serve import generate_signature, verify_signature
+from wagtail.wagtailimages.views.serve import ServeView, generate_signature, verify_signature
 
 from .utils import Image, get_test_image_file
 
@@ -273,11 +273,9 @@ class TestFrontendServeView(TestCase):
 
         self.assertRedirects(response, expected_redirect_url, status_code=301, fetch_redirect_response=False)
 
-    def test_get_with_unknown_action(self):
-        signature = generate_signature(self.image.id, 'fill-800x600')
-
+    def test_init_with_unknown_action_raises_error(self):
         with self.assertRaises(ImproperlyConfigured):
-            self.client.get(reverse('wagtailimages_serve_action_unknown', args=(signature, self.image.id, 'fill-800x600')))
+            ServeView.as_view(action='unknown')
 
     def test_get_with_custom_key(self):
         """
diff --git a/wagtail/wagtailimages/tests/urls.py b/wagtail/wagtailimages/tests/urls.py
index cf781c8f1a..e8f82bbb0e 100644
--- a/wagtail/wagtailimages/tests/urls.py
+++ b/wagtail/wagtailimages/tests/urls.py
@@ -8,6 +8,5 @@ from wagtail.wagtailimages.views.serve import ServeView
 urlpatterns = [
     url(r'^actions/serve/(.*)/(\d*)/(.*)/[^/]*', ServeView.as_view(action='serve'), name='wagtailimages_serve_action_serve'),
     url(r'^actions/redirect/(.*)/(\d*)/(.*)/[^/]*', ServeView.as_view(action='redirect'), name='wagtailimages_serve_action_redirect'),
-    url(r'^actions/unknown/(.*)/(\d*)/(.*)/[^/]*', ServeView.as_view(action='unknown'), name='wagtailimages_serve_action_unknown'),
     url(r'^custom_key/(.*)/(\d*)/(.*)/[^/]*', ServeView.as_view(key='custom'), name='wagtailimages_serve_custom_key'),
 ]
diff --git a/wagtail/wagtailimages/views/serve.py b/wagtail/wagtailimages/views/serve.py
index 82896a2932..6560c95042 100644
--- a/wagtail/wagtailimages/views/serve.py
+++ b/wagtail/wagtailimages/views/serve.py
@@ -10,6 +10,7 @@ from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured, PermissionDenied
 from django.http import HttpResponse, HttpResponsePermanentRedirect, StreamingHttpResponse
 from django.shortcuts import get_object_or_404
+from django.utils.decorators import classonlymethod
 from django.utils.six import text_type
 from django.views.generic import View
 
@@ -40,6 +41,14 @@ class ServeView(View):
     action = 'serve'
     key = None
 
+    @classonlymethod
+    def as_view(cls, **initkwargs):
+        if 'action' in initkwargs:
+            if initkwargs['action'] not in ['serve', 'redirect']:
+                raise ImproperlyConfigured("ServeView action must be either 'serve' or 'redirect'")
+
+        return super(ServeView, cls).as_view(**initkwargs)
+
     def get(self, request, signature, image_id, filter_spec):
         if not verify_signature(signature.encode(), image_id, filter_spec, key=self.key):
             raise PermissionDenied
@@ -63,8 +72,6 @@ class ServeView(View):
         elif self.action == 'redirect':
             # Redirect to the file's public location
             return HttpResponsePermanentRedirect(rendition.url)
-        else:
-            raise ImproperlyConfigured("ServeView action must be either 'serve' or 'redirect'")
 
 
 serve = ServeView.as_view()