ABAP CDS - Domain conversion routine not used when cast in concat/concat_with_space

[HenrikD]

I have an ABAP CDS View where I need to combine two fields from table MARA, but for some reason the conversion routine is not kicking in for EAN11. Works just fine for casting the field alone, but not when used in CONCAT/CONCAT_WITH_SPACE.

define view YDEMO as select from mara as _master {
  cast(_master.ean11 as EAN11) as EAN,
  concat_with_space( cast( _master.ean11 as EAN11), 'test', 1 ) as test
}

The example returns:

EAN: 0012345678912

Test: 12345678912 test

The EAN code in test has not been converted and missing the leading zeros.

SAP System: 7.50.22 with Oracle 19.14.

What have I misunderstood? Shouldn't it work?

Regards,

Henrik