Apenas adicionado um comentário.

sigi/urls.py

@@ -2,9 +2,11 @@ from django.conf import settings
 from django.conf.urls.defaults import *
 from django.contrib import databrowse
 from django.db.models import get_models
-import sigi.admin.filterspecs
 from sigi import sites
 
+# register admin filters
+import sigi.admin.filterspecs
+
 map(databrowse.site.register, get_models())
 
 urlpatterns = patterns(