Why do I lose port information if I open my S-Function block?

Dear Matlab,

I have ceated an S-Function block by "legacy_code" command(s), see in the attached "m" file. It was with success. Then I extended the block with the following definitions in "Edit Mask/Icon & Ports":

 fprintf('ex_sf_cc');
port_label('input', 1, 'pDemCoor');
port_label('input', 2, 'pProv2');
port_label('input', 3, 'pAbsEpm');
port_label('input', 4, 'pEpm');
port_label('input', 5, 'wheelState');
port_label('output', 1, 'pDemEpm');
port_label('output', 2, 'pBrake');
port_label('output', 3, 'pLimPcvBiuld');
port_label('output', 4, 'pLimPcvExhaust');
port_label('output', 5, 'pcvDuty');
port_label('output', 6, 'LauschArray');

As You can see: this is just the description for the ports of the S-Function block. I have saved the block, also attached.

The problem is, that each time I open the block (I mean double click on the block to verify the parameters), or I go with "Edit mask" all these descriptions get lost, they will be replaced by the standard description (S-Function name). Similar question I have found here: Block copy, old question. Could You help me to solve the problem? I'm using Matlab 2013b.

Thanks

Gábor