5.7.X : problem with attributed variables and memberchk ?

Hello, I found something strange, I am wondering if there isn't a
problem with attributed variables (at least clpfd ones) and
memberchk (and maybe other predicates ...).

I am using current git for 5.7.X swi-prolog, and if I run the
following commands, this is the results I get :

Welcome to SWI-Prolog (Multi-threaded, 32 bits, Version
5.7.1-31-g8d293e0-DIRTY)
Copyright (c) 1990-2008 University of Amsterdam.
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free
software,
and you are welcome to redistribute it under certain conditions.
Please visit http://www.swi-prolog.org for details.

?- use_module(library(clpfd)).
%  library(error) compiled into error 0.00 sec, 9,704 bytes
% library(clpfd) compiled into clpfd 0.05 sec, 220,728 bytes
true.

?- A in 0..5, B in 6..7, member(A, [B, C]).
A = C,
C in 0..5,
B in 6..7 ;
false.

?- A in 0..5, B in 6..7, memberchk(A, [B, C]).
false.

Shouldn't the last one return :
A = C,
C in 0..5,
B in 6..7.

?

I hope I do not forget something important and that my question is
not dumb :)

Thanks you,

Victor