Sleep wm_schedule not working at all

The next piece of code (extracted from WM wiki) is not working:

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wm_schedule
{
{ action='tween', tween='rotate_sec', from=0, to=90, duration=1, easing=outQuad },
{ action='sleep', sleep=1 },
{ action='run_function', run_function=myfunc },
{ action='tween', tween='rotate_sec', from=90, to=0, duration=1, easing=outQuad },
}
-----------------------------------

The actions 1, 3 and 4 are executed at the same time.
The action 2 (sleep) is not executed at all.