--- a/configure.ac
+++ b/configure.ac
@@ -62,7 +62,7 @@ LTDL_INIT
 m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES([yes])], [AC_SUBST([AM_DEFAULT_VERBOSITY],1)])
 
 
-CFLAGS="$LTDLINCL `$GUILECONFIG compile`"
+CFLAGS="$CFLAGS $LTDLINCL `$GUILECONFIG compile`"
 LIBS="$LIBLTDL `$GUILECONFIG link`"
 GUILE_SITE=`$GUILECONFIG info sitedir`