libtest_la_LIBADD bug?

[NFRA visitor]

Dear libtool maintainers,

I'm trying to include a convenience library (which is in a subdirectory 
of the main library)  into the main library. This isn't working for me.

intention:

convenience library: src/sub/testsub.c src/sub/testsub.h: compiled into 
libtestsub.la
main library: src/test.c src/test.h: together with libtestsub.la: 
compiled into libtest.la

The bug is that the object testsub.o from sub/libtestsub.la is not 
included in libtest.la (or actually libtest.a).

I use the following line in src/Makefile.am to do this:

libtest_la_LIBADD = sub/libtestsub.la

I've included a libtoolbug.tgz which demonstrates the problem:

tar zxvf libtoolbug.tgz
cd libtoolbug
/bootstrap
/bootstrap
mkdir build
cd build
./configure
make
ar t src/.libs/libtest.a
test.o

BUG: the testsub.o object is not included in the library.

Note that I've added the line AC_DISABLE_SHARED in configure.in 
otherwise this wouldn't be possible at all.

The question is: Is this really a bug or should I be doing this a 
different way?

Your help is greatly appreciated.

Regards,
Klaas Jan Wierenga

p.s.: ./config.guess returns
i686-pc-linux-gnu

libtoolbug.tgz
Description: Binary data