diff --git a/activitystream/filters.py b/activitystream/filters.py
index e5ef4bae..994d59c2 100644
--- a/activitystream/filters.py
+++ b/activitystream/filters.py
@@ -1,12 +1,12 @@
-from django_filters import NumberFilter, FilterSet
+from django_filters import CharFilter, FilterSet
 from wagtail.models import Page
 
 
 class ActivityStreamCMSContentFilter(FilterSet):
-    after = NumberFilter(method='filter_after')
+    after = CharFilter(method='filter_after')
 
     def filter_after(self, queryset, name, value):
-        value = value or 0
+        value = value or '0'
         return queryset.filter(id__gt=value)
 
     class Meta: