_SOURCES files in sub-directories lead to make distdir failure

[netfab]

Hi,

I'm using automake-1.15.1 to build a project using recursive makefiles.

Into that project, there's a subdirectory to build a library using
libtool-2.4.6. The source code of this library is organized into
sub-directories, like this :
>       mylib/makefile.am
>       mylib/aaa.cpp
>       mylib/aaa.h
>       mylib/foo/bbb.cpp
>       mylib/foo/bbb.h
>       mylib/bar/ccc.cpp
>       mylib/bar/ccc.h


The makefile.am for this lib contains :
> libmyLIB_la_SOURCES = \
>           aaa.cpp     aaa.h \
>       foo/bbb.cpp foo/bbb.h \
>       bar/ccc.cpp bar/ccc.h


I'm initializing automake with :
> AM_INIT_AUTOMAKE([subdir-objects])


When building the whole project, it works fine.
However, when running :
> make distcheck


Is fails like following, and I don't see how to fix this :
> make[5]: Entering directory '/path/to/project/build/src/lib/mylib'
> make[5]: *** No rule to make target 'foo/bbb.h ', needed by 'distdir'. Stop.

Any advice ? Thanks.