Invalid gif produced from reverse order frames

[potpath]

gifsicle commit e5e6c72
Image from https://en.wikipedia.org/wiki/File:Rotating_fountain_coriolis_effect02.gif

Here is the output from:
gifsicle tmp.gif "#-1-0" > tmp-reverse.gif

This issue appears in some but not all gif.
For example, running the same command to https://commons.wikimedia.org/wiki/File:Pethidine3Dan.gif results in correct gif.

[iirelu]

It's because the gif is optimised. Use gifsicle -U tmp.gif "#-1-0" > tmp-reverse.gif and it will work fine.

[potpath]

It works now. Thanks!