Different result than expected when poking to screen

[emook]

Hello,

In normal basic we can do this following code :

Code:

10 BORDER 0: PAPER 0: INK 6: CLS
20 FOR i=1 TO 7
30 FOR y=0 TO 21
40 FOR x=0 TO 31
50 LET l=22528+x+y*32
60 POKE l,8*i
70 NEXT x
80 NEXT y
90 NEXT i

To fill the screen with the desired colour (I know this example seems pointless, but the same method to poke a screen char is used quite a bit for me)

however, in ZXB it only seems to pokes to the top third of the screen :

Code:

border 0
paper 0
ink 6
cls

dim i as ubyte
dim x as ubyte
dim y as ubyte
dim l as uinteger

FOR i=1 TO 6
FOR y=0 TO 23
FOR x=0 TO 31
l=22528+x+y*32
POKE l,8*i
NEXT
NEXT
NEXT

Anyone know what I am doing wrong here?

Thanks!