diff --git a/src/argus/htmx/timeslot/views.py b/src/argus/htmx/timeslot/views.py
index 160c3d81b..ae3d6e663 100644
--- a/src/argus/htmx/timeslot/views.py
+++ b/src/argus/htmx/timeslot/views.py
@@ -34,11 +34,14 @@ class TimeslotMixin:
     model = Timeslot
     prefix = "timeslot"
 
-    def get_prefix(self):
-        if self.object and self.object.pk:
-            return self.prefix + f"-{self.object.pk}"
+    def _get_prefix(self, pk):
+        if pk:
+            return self.prefix + f"-{pk}"
         return self.prefix
 
+    def get_prefix(self):
+        return self._get_prefix(getattr(self.object, "pk", None))
+
     def get_queryset(self):
         qs = super().get_queryset().prefetch_related("time_recurrences")
         return qs.filter(user_id=self.request.user.id)
@@ -90,7 +93,7 @@ def get_context_data(self, **kwargs):
         context = super().get_context_data(**kwargs)
         forms = []
         for obj in self.get_queryset():
-            form = TimeslotForm(None, instance=obj)
+            form = TimeslotForm(None, instance=obj, prefix=self._get_prefix(obj.pk))
             formset = make_timerecurrence_formset(timeslot=obj)
             forms.append({"form": form, "formset": formset})
         context["form_list"] = forms