How to use ...anim_speed?

LVGL version v8.2

How to use …anim_speed ?

I create a BAR and change the values.

lv_bar_set_value(bar, 50, LV_ANIM_ON);

But when I use anim_time it works.

lv_obj_set_style_anim_time(bar, 1000, 0);

When I use anim_speed it doesn’t work. Why?

lv_obj_set_style_anim_speed(bar, 10, 0);

What am I doing wrong?