diff --git a/src/argus/htmx/incident/views.py b/src/argus/htmx/incident/views.py
index 173c8fb2e..ac4c792e1 100644
--- a/src/argus/htmx/incident/views.py
+++ b/src/argus/htmx/incident/views.py
@@ -120,13 +120,14 @@ def create_filter(request: HtmxHttpRequest):
 @require_GET
 def filter_select(request: HtmxHttpRequest):
     filter_id = request.GET.get("filter", None)
-    request.session["selected_filter"] = filter_id
     if filter_id and get_object_or_404(Filter, id=filter_id):
+        request.session["selected_filter"] = filter_id
         incident_list_filter = get_filter_function()
         filter_form, _ = incident_list_filter(request, None)
         context = {"filter_form": filter_form}
         return render(request, "htmx/incident/_incident_filterbox.html", context=context)
     else:
+        request.session["selected_filter"] = None
         if request.htmx.trigger:
             return reswap(HttpResponse(), "none")
         else: