Get always the same picture set at startup with `randomize`

[ChoppinBlockParty]

I have a feh command run on startup by my window manager:

feh --no-fehbg -Z --recursive --bg-fill --randomize ${SCRIPT_DIR}/wallpapers

I wonder why it always set the same picture. I have 4 pictures in this directory. When I run the same command manually multiple times it does produce random results.

Thank you.