diff --git a/m4/moo-lua.m4 b/m4/moo-lua.m4
index d255a96c..97699f8e 100644
--- a/m4/moo-lua.m4
+++ b/m4/moo-lua.m4
@@ -2,7 +2,6 @@ AC_DEFUN([MOO_LUA],[
   AC_REQUIRE([MOO_AC_CHECK_OS])
 
   MOO_LUA_CFLAGS=
-  _moo_ac_have_posix_spawn=no
 
   if $MOO_BUILD_LUA; then
     if test "x$MOO_OS_DARWIN" = "xyes"; then
@@ -10,11 +9,7 @@ AC_DEFUN([MOO_LUA],[
     elif test "x$MOO_OS_MINGW" != "xyes"; then
       MOO_LUA_CFLAGS="-DLUA_USE_POSIX -DLUA_USE_DLOPEN"
     fi
-
-    # for lua-ex
-    AC_CHECK_FUNCS(posix_spawn,[_moo_ac_have_posix_spawn=yes])
   fi
 
-  AM_CONDITIONAL(HAVE_POSIX_SPAWN,[test $_moo_ac_have_posix_spawn = yes])
   AC_SUBST([MOO_LUA_CFLAGS])
 ])