-DX_PROG_FLEX([], [], [FLEX=false])
-DX_PROG_BISON([], [], [BISON=false])
+DX_PROG_FLEX([], [have_flex=yes], [have_flex=no])
+AM_CONDITIONAL([HAVE_FLEX], [test x"$have_flex" = x"yes"])
+
+DX_PROG_BISON([], [have_bison=yes], [have_bison=no])
+AM_CONDITIONAL([HAVE_BISON], [test x"$have_bison" = x"yes"])
+