Deserialization of body broken based on module load order

Given the following module Foo:

package Foo;

use Dancer2;

use strict;
use warnings;

set serializer => 'JSON';

# curl -d '{ "key": [ "value" ] }' -H 'Content-Type: application/json' -H 'Expect:' -X POST "http://localhost:5000/"
post '/' => sub {
	use Data::Dumper;
	print STDERR Dumper['request',request];
	print STDERR Dumper['request-params',request->params];
	print STDERR Dumper['request-body',request->body];

	return param('key');
};

This works:

#!/usr/bin/env perl

use lib '/tmp/dancer-issue';

use Foo;
use Dancer2;

dance;

Output:

$ curl -d '{ "key": [ "value" ] }' -H 'Content-Type: application/json' -H 'Expect:' -X POST "http://localhost:5000/"
["value"]

This does not work:

#!/usr/bin/env perl

use lib '/tmp/dancer-issue';

use Dancer2;
use Foo;

dance;

Output:

$ curl -d '{ "key": [ "value" ] }' -H 'Content-Type: application/json' -H 'Expect:' -X POST "http://localhost:5000/"
$

What's strange is that set serializer in the Foo module does affect the serialization of returned values from routes - so it's not as if it has no effect. It's just broken for deserialization of anything sent via the body.

The module load order in the psgi wrapper is the only thing that changes. I've also tested this under Apache rather than plackup and the repro is the same.

Versions:

$ rpm -q perl-Dancer2 perl-Plack
perl-Dancer2-0.204002-1.noarch
perl-Plack-0.9979-2.el6.rfx.noarch

Reproduce the issue with the Foo module and PSGI wrapper, switching only the order of use Dancer2 and use Foo. Compare body deserialization and returned route values in both cases, then trace the serializer setup used by the request body. Done means JSON request bodies deserialize consistently regardless of module load order.