diff --git a/django/contrib/admin/views/main.py b/django/contrib/admin/views/main.py
index 324841a669..df6b724d07 100644
--- a/django/contrib/admin/views/main.py
+++ b/django/contrib/admin/views/main.py
@@ -226,7 +226,7 @@ index = staff_member_required(never_cache(index))
 def add_stage(request, app_label, model_name, show_delete=False, form_url='', post_url=None, post_url_continue='../%s/', object_id_override=None):
     model = models.get_model(app_label, model_name)
     if model is None:
-        raise Http404, "App %r, model %r, not found" % (app_label, model_name)
+        raise Http404("App %r, model %r, not found" % (app_label, model_name))
     opts = model._meta
 
     if not request.user.has_perm(app_label + '.' + opts.get_add_permission()):
@@ -302,7 +302,7 @@ def change_stage(request, app_label, model_name, object_id):
     model = models.get_model(app_label, model_name)
     object_id = unquote(object_id)
     if model is None:
-        raise Http404, "App %r, model %r, not found" % (app_label, model_name)
+        raise Http404("App %r, model %r, not found" % (app_label, model_name))
     opts = model._meta
 
     if not request.user.has_perm(app_label + '.' + opts.get_change_permission()):
@@ -313,8 +313,8 @@ def change_stage(request, app_label, model_name, object_id):
 
     try:
         manipulator = model.ChangeManipulator(object_id)
-    except ObjectDoesNotExist:
-        raise Http404
+    except model.DoesNotExist:
+        raise Http404('%s object with primary key %r does not exist' % (model_name, object_id))
 
     if request.POST:
         new_data = request.POST.copy()
@@ -490,7 +490,7 @@ def delete_stage(request, app_label, model_name, object_id):
     model = models.get_model(app_label, model_name)
     object_id = unquote(object_id)
     if model is None:
-        raise Http404, "App %r, model %r, not found" % (app_label, model_name)
+        raise Http404("App %r, model %r, not found" % (app_label, model_name))
     opts = model._meta
     if not request.user.has_perm(app_label + '.' + opts.get_delete_permission()):
         raise PermissionDenied
@@ -527,7 +527,7 @@ def history(request, app_label, model_name, object_id):
     model = models.get_model(app_label, model_name)
     object_id = unquote(object_id)
     if model is None:
-        raise Http404, "App %r, model %r, not found" % (app_label, model_name)
+        raise Http404("App %r, model %r, not found" % (app_label, model_name))
     action_list = LogEntry.objects.filter(object_id=object_id,
         content_type__id__exact=ContentType.objects.get_for_model(model).id).select_related().order_by('action_time')
     # If no history was found, see whether this object even exists.
@@ -743,7 +743,7 @@ class ChangeList(object):
 def change_list(request, app_label, model_name):
     model = models.get_model(app_label, model_name)
     if model is None:
-        raise Http404, "App %r, model %r, not found" % (app_label, model_name)
+        raise Http404("App %r, model %r, not found" % (app_label, model_name))
     if not request.user.has_perm(app_label + '.' + model._meta.get_change_permission()):
         raise PermissionDenied
     try: