When trying to instantiate a list element in a record my program does not work. I get the following error in the declaration of the subtype list_unbounded: hear.adb:25:65: error: prefix must not be a generic package hear.adb:25:65: error: use package instantiation as prefix instead hear.adb:25:70: error: incorrect constraint for this kind of type gnatmake: "hear.adb" compilation error

Procedure hear is:
    ind : Integer;
    Subtype List_Unbounded is Ada.Containers.Doubly_Linked_Lists.List(ELement_Type => Ada.Strings.UNbounded.Unbounded_String);
    Type T_Node is record
        Name : Ada.Strings.Unbounded.UNbounded_String;
        N_List : List_Unbounded;
    end record;
begin
(...)