Installed vs built library

[Luigi Ballabio]

Hi all,
        it's probably something stupid I'm doing. However, 
here's the problem. Inside a project I'm building a shared
library in a sub-directory and a test-suite executable in 
another. The related lines of the respective Makefile.am are

lib_LTLIBRARIES = libFoo.la

and 

bin_PROGRAMS = foo-test-suite
foo_test_suite_LDADD = ../lib/libFoo.la
TESTS = foo-test-suite

Now, if I don't have a previous version of libFoo installed,
make && make check works fine. However, if this is not the case, 
running 'make check' causes the installed library to be loaded
rather than the newly-built one.

What am I doing wrong?

Thanks,
        Luigi

P.S. Almost forgetting: libtool 1.4.3, automake 1.7.6, 
autoconf 2.57