I'm trying to modify a named range in an existing spreadsheet, like so:

HSSFName name = wb.getNameAt(0);
System.out.println("name:"+name.getNameName()+" "+name.getReference()
+" "+name.getSheetName()); 
name.setReference("Verkopen!$A$1:$C$36");
System.out.println("name:"+name.getNameName()+" "+name.getReference()
+" "+name.getSheetName()); 

Outputs:
name:VerkoopData Verkopen!$A$1:$C$19 Verkopen
name:VerkoopData Verkopen!$IU$1:$C$36 Verkopen

The first (unmodified) reference is OK, the second (modified) is obviously 
wrong. 
       
TIA