Cannot compile nested generic type with constraint

[NN---]

Same code in C# compiles fine.

public class AA[T]
{
  public class B[U] : AA[U] where U : B[U] {}
}

error: internal compiler error: assertion ``self_type != null'' failed in file ncc\hierarchy\TypeInfo.n, line 1081: AA.B
   at Nemerle.Compiler.TypeInfo.NestingSubst(TypeInfo parent)
   at Nemerle.Compiler.TypeVarEnv.bind_simple_named_type(GlobalEnv env, TypeBuilder currentType, Name name, list`1 idl, list`1 args, Location loc)
   at Nemerle.Compiler.TypeVarEnv._N_type_class_125915(_N_closureOf_Bind_125881 _N_Bind_cp_125914, PExpr tyexpr)
   at Nemerle.Compiler.TypeVarEnv._N_f2_125909(_N_closureOf_Bind_125881 _N_Bind_cp_125908, PExpr t, Boolean allow_ref)
   at Nemerle.Compiler.TypeVarEnv._N_f__125900.apply(PExpr t)
   at Nemerle.Compiler.TypeVarEnv.Bind(GlobalEnv env, TypeBuilder currentType, PExpr t, Boolean allow_tyvars, Boolean check_parms)
   at Nemerle.Compiler.TypeVarEnv.BindFixedType(GlobalEnv env, TypeBuilder currentType, PExpr t, Boolean check_parms)
   at Nemerle.Compiler.TypeVarEnv.AddTyparms(GlobalEnv env, Typarms tp, TypeBuilder currentType, Boolean check_parms)
   at Nemerle.Compiler.TypeBuilder.make_tyenvs()
   at Nemerle.Compiler.TypeBuilder.make_tyenvs()
   at Nemerle.Compiler.TypesManager.Run()
   at Nemerle.Compiler.ManagerClass.Run()
   at Nemerle.CommandlineCompiler.MainClass.main_with_catching()