[Koha] new authorized value for damaged: tinyint vs int

Hi, I've defined a new authorized value for the DAMAGED category. In my database, this corresponds to id = 256 in the authorised_values table, where id is an int(11). However, when I try to select that authorized value for a particular item, my choice is not recorded. I noticed that items.damaged is described as tinyint(1). In fact, if I try to update items manually and set 256, this is automatically converted into 127. How can I solve this problem? Is it a bug I should report, or rather a database upgrade in my system which did not take place correctly? Many thanks and best regards, Giuseppe.