#OIL, 12 bytes

Here in annotated form (remove anything but numbers to run):

1 # copy
-1 # from line -1 (containing, by default, a 0)
6 # to line 6 (the first line after the last line) %
8 # increment
2 # line 2 (marked with %)
6 # goto (since the next line will now be 0, go to line 0)

Even though seemingly nothing changes (lines are 0 by default and are being set to 0), internally, there's a difference between an unallocated line and a line with an explicit 0 in it.

OIL, 12 bytes

Here in annotated form (remove anything but numbers to run):

1 # copy
-1 # from line -1 (containing, by default, a 0)
6 # to line 6 (the first line after the last line) %
8 # increment
2 # line 2 (marked with %)
6 # goto (since the next line will now be 0, go to line 0)

Even though seemingly nothing changes (lines are 0 by default and are being set to 0), internally, there's a difference between an unallocated line and a line with an explicit 0 in it.