@Place - strange error!

[Jürgen H. Havix]

Hello,
I used lout-vers. 3.25 with a lot of Graphics, placed by the '@Place'
symbol, including defined values like: def @aTop {1c}, so that you can
place a bunch of graphic in the same manner by changing only one value.
When I switched to 3.28 (Debian), I got a lot of errors, which boiled
down to a unit question:
The following code works, if you take the (depricated) unit ' cm' for the
definition: def @ptop {10.9 cm}. It fails with a postscript-error, if you
take any other unit like @ptop {10.9c}.
It also works of course, if you circumvent the definition and put the value
directly into the @Place - part.
Can anybody lighten this behavior?
Thanks, George

@Include {doc}
import @BasicSetup
# def @ptop {10.9c }  # This definition with unit 'c' fails !
def @ptop {10.9 cm }  # This definition with unit ' cm'works !
def @Head
{
@Place
x { left + 0.6c  }
# y { top - @ptop }  #postscript-error : Error: /undefined in 10.9c
y { top - 10.9c }    # This works!
 {This should show up}
}

@Document
@InitialFont { Helvetica Base 11p }
@InitialBreak { adjust 1.0fx hyphen }
@InitialSpace { lout }
@InitialLanguage { German }
@PageOrientation { Portrait }
@PageHeaders { Simple }
@FirstPageNumber { 1 }
@ColumnNumber { 1 }
@OptimizePages { No }
@Unpaginated { No }
//
@Text @Begin
@LLP
@Head
@End @Text