autoconf search for ClearSilver.h fails

Hi everybody!

I have a strange problem.

I wanted to autoconf a program i wrote which utilizes ClearSilver.

<snip file=configure.ac>

AC_INIT([quicksilver],[0.0.1],[[email protected]])
AC_CONFIG_AUX_DIR([build-aux])
AM_INIT_AUTOMAKE([-Wall -Werror])
AC_PROG_CC
AC_CHECK_HEADERS([sys/syslog.h ClearSilver/ClearSilver.h])
AC_CONFIG_HEADERS([config.h])
AC_CONFIG_FILES([Makefile src/Makefile])
AC_OUTPUT

</snip>

For whatever reason, ClearSilver.h is not found, though syslog.h is (I
actually tried with _v_a_r_i_o_u_s_ files.

Thanks in advance,

Markus