for/next/step - did i find a bug?

[nitrofurano]

i don't know if this is a bug, or if i'm defining variable kind wrongly ('j' is not stopping at '0') - thanks in advance!

Code:

border 0:cls
dim i,j as uinteger
for i=0 to 6143 step 3
  poke 16384+0+i,128+16+2
  poke 16384+1+i,64+8+1
  poke 16384+2+i,32+4
  next i
lp01:
for j=16384 to 0 step -32
  print at 0,0;j;" "
  pause 1
  for i=0 to 767
    poke 16384+6144+i,peek(i+j) band 127
    next i
  next j
goto lp01