diff --git a/src/agenda_culturel/filters.py b/src/agenda_culturel/filters.py
index 93dd88d..cb90b9e 100644
--- a/src/agenda_culturel/filters.py
+++ b/src/agenda_culturel/filters.py
@@ -130,13 +130,18 @@ class EventFilter(django_filters.FilterSet):
             if len(params['category']) == 0:
                 return url
             else:
-                category = Category.objects.filter(pk=params['category'][0]).first()
+                cat_id = params['category'][0]
                 del params["category"]
                 url = parsed_url._replace(query=urlencode(params, doseq=True)).geturl()
-                if category is None:
-                    return url
+                if cat_id.isdigit():
+                    category = Category.objects.filter(pk=cat_id).first()
+                    if category is None:
+                        return url
+                    else:
+                        return "/cat:" + category.slug + url
                 else:
-                    return "/cat:" + category.slug + url
+                    return url
+
 
     def filter_recurrences(self, queryset, name, value):
         # construct the full lookup expression