diff --git a/event/views.py b/event/views.py
index 5a5d3df..6e29dde 100644
--- a/event/views.py
+++ b/event/views.py
@@ -52,6 +52,12 @@ class EnrolActivityView(LoginRequiredMixin, View):
         else:
             success = False
         if "ajax" in request.GET:
+            if request.GET["ajax"] == "json":
+                enrols = activity.staff
+                return JsonResponse({
+                    "enrolled": enrols.filter(id=request.user.id).exists(),
+                    "number": enrols.count(),
+                })
             return render(request, "event/activity_summary.html",
                           {"activity": activity})
         return HttpResponseRedirect(reverse("event:activity", kwargs={"pk":pk}))