create a linux server with 0 swap

create an item for example system.swap.size[,free] 

the item will become unsupported and return

system.swap.size[,free] [m|ZBX_NOTSUPPORTED] [Cannot be calculated because swap file size is 0.]

so preprocessing cant be used 

i would have expected to have seen the value of 0

as this is what linux returns to me when running free 

free -m
total used free shared buff/cache available
Mem: 1998 408 509 123 1081 1283
Swap: 0 0 0