_NET_WM_STATE is ATOM[] not ATOM, a list of window state hints, so check all of the atoms, not just the first one See EWMH specifcation, section "Application Window Properties" v2: Actually use [] on the returned atom data Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk> Reviewed-by: Colin Harrison <colin.harrison@virgin.net>