AC_ARG_VAR([FLEX], [Command to invoke flex. Defaults to flex.])
AC_ARG_VAR([FLEXFLAGS], [Additional options to pass to flex.])
-AC_CHECK_PROGS([FLEX], [flex], [$MISSING flex])
+AC_CHECK_PROGS([FLEX], [flex], [flex])
AC_ARG_VAR([BISON], [Command to invoke GNU Bison. Defaults to bison.])
AC_ARG_VAR([BISONFLAGS], [Additional options to pass to Bison.])