   # to clear a group gate
   #
   delete "/flags/:name/groups/:group_name" do
-    flag_name = String.to_atom(name)
-    group_name = String.to_atom(group_name)
+    flag_name = String.to_existing_atom(name)
+    group_name = String.to_existing_atom(group_name)
 
     FunWithFlags.clear(flag_name, for_group: group_name)
 

  #
  patch "/flags/:name/groups/:group_name" do
    enabled = Utils.parse_bool(conn.params["enabled"])
    flag_name = String.to_atom(name)
    group_name = String.to_atom(group_name)

    if enabled do

  #
  patch "/flags/:name/boolean" do
    enabled = Utils.parse_bool(conn.params["enabled"])
    flag_name = String.to_existing_atom(name)

    if enabled do
      FunWithFlags.enable(flag_name)
