Formular checkbox behaves like radiobutton

[AndySilvia]

Hi!

I made a little test-task/-formular to test the different field types and there I fell over a strange thing:

Step-file-excerpt:

• name: Feld4
  type: checkbox
  label: Feld4-checkbox
  values:
  - label: Check1
  value: Check1
  - label: Check2
  value: Check2

Task-excerpt:
my $fcmdb = get cmdb "testform";
my $feld4 = $fcmdb->{Feld4};
say "Feld4: ";
say Dumper($feld4);

Problem:
If I don't check a value, $feld4 is correctly undef, If I check first value feld4 is correctly "Check1", if I check second value feld4 is correctly "Check2", but if I check both values, feld4 is "Check1" too...

Log-excerpts:

Checked first value:
Feld4:
$VAR1 = 'Check1';

Checked second value:
Feld4:
$VAR1 = 'Check2';

Checked none:
Feld4:
$VAR1 = undef;

Checked both:
Feld4:
$VAR1 = 'Check1';

Even if I make
say Dumper($fcmdb);

It logs:
$VAR1 = {
'Feld4' => 'Check1'
};

Am I doing something wrong or is there some kind of failure?

Thanks for clarification in advance!

Bye,

AndySilvia