Why does changing a Moose attributes' properties remove the around modifier

[mcrose]

Why does the following code not work for the derived class? Changing the properties of the base class' accessor removes the around modifier defined in the base class. When I simply inherit the base class without modifying it, however, the around modifier fires off properly.

I know I can work around this, but I'm surprised it doesn't work as-is.

use strict;
use warnings;
use 5.010;

package My::Base;
use Moose;

has 'attr' => (is => 'rw', isa => 'Str', required => 1);

around 'attr' => sub {
  my $orig = shift;
  my $self = shift;
  
  my $response = $self->$orig(@_);
  return "The value of attr is '$response'"
};

package My::Derived;
use Moose;

extends 'My::Base';

has '+attr' => (required => 0, lazy_build => 1);

sub _build_attr {
  return "default value";
}

package My::Inherited;
use Moose;

extends 'My::Base';

package main;
use Test::More tests => 9;
use Test::Exception;

throws_ok {My::Base->new()} qr/Attribute \(attr\) is required/, q/base
+ requires 'attr' at construction/;
my $base = new_ok('My::Base' => [attr => 'constructor value']);
cmp_ok($base->attr, 'eq', "The value of attr is 'constructor value'", 
+'base is correct');
lives_ok {My::Derived->new()} q/derived doesn't require 'attr' at cons
+truction/;
my $der = new_ok('My::Derived');
cmp_ok($der->attr, 'eq', "The value of attr is 'default value'", 'deri
+ved is correct');
throws_ok {My::Base->new()} qr/Attribute \(attr\) is required/, q/inhe
+rited requires 'attr' at construction/;
my $inh = new_ok('My::Inherited' => [attr => 'constructor value']);
cmp_ok($inh->attr, 'eq', "The value of attr is 'constructor value'", '
+inherited is correct');

The above gives the following output:

1..9
ok 1 - base requires 'attr' at construction
ok 2 - The object isa My::Base
ok 3 - base is correct
ok 4 - derived doesn't require 'attr' at construction
ok 5 - The object isa My::Derived
not ok 6 - derived is correct
#   Failed test 'derived is correct'
#   at foobar.pl line 43.
#          got: 'default value'
#     expected: 'The value of attr is 'default value''
ok 7 - inherited requires 'attr' at construction
ok 8 - The object isa My::Inherited
ok 9 - inherited is correct
# Looks like you failed 1 test of 9.