Guile-CV: Not a GRAY, RGB nor an RGBA image "sand.tif"

[Daniele]

Hello, I've installed guile-cv on debian buster following the
instructions in the manual, when I try to use it I get this error
though:

scheme@(guile-user)> ,use (cv)
scheme@(guile-user)> (im-load "sand.tif")
ERROR: In procedure scm-error:
ERROR: Not a GRAY, RGB nor an RGBA image "sand.tif"

Any idea what might be the cause?

Daniele