diff --git a/helpdesk/apps.py b/helpdesk/apps.py
index d316d314..de9d8537 100644
--- a/helpdesk/apps.py
+++ b/helpdesk/apps.py
@@ -11,3 +11,7 @@ class HelpdeskConfig(AppConfig):
 
     def ready(self):
         from . import webhooks # noqa: F401
+
+        from django.db.models.fields import Field
+        from helpdesk.orm_operators import NotIn
+        Field.register_lookup(NotIn)
diff --git a/helpdesk/orm_operators.py b/helpdesk/orm_operators.py
new file mode 100644
index 00000000..46c26ff3
--- /dev/null
+++ b/helpdesk/orm_operators.py
@@ -0,0 +1,7 @@
+from django.db.models.lookups import In
+
+class NotIn(In):
+    lookup_name = "not_in"
+
+    def get_rhs_op(self, connection, rhs):
+        return "NOT IN %s" % rhs
diff --git a/helpdesk/views/staff.py b/helpdesk/views/staff.py
index 0f230583..b95d6569 100644
--- a/helpdesk/views/staff.py
+++ b/helpdesk/views/staff.py
@@ -424,11 +424,9 @@ def view_ticket(request, ticket_id):
 
         return redirect('helpdesk:edit_ticket_checklist', ticket.id, checklist.id)
 
-    open_dependencies = ticket.ticketdependency.filter(depends_on__status__in=Ticket.OPEN_STATUSES)
-    dependencies = [d for d in itertools.chain(
-        open_dependencies,
-        ticket.ticketdependency.all().difference(open_dependencies)
-    )]
+    # Open tickets on top
+    dependencies = list(ticket.ticketdependency.filter(depends_on__status__in=Ticket.OPEN_STATUSES)) \
+        + list(ticket.ticketdependency.filter(depends_on__status__not_in=Ticket.OPEN_STATUSES))
     
     return render(request, 'helpdesk/ticket.html', {
         'ticket': ticket,