diff --git a/common/luaobject.h b/common/luaobject.h
index 77ec6ba..c3e1f05 100644
--- a/common/luaobject.h
+++ b/common/luaobject.h
@@ -195,7 +195,7 @@ int luaA_object_emit_signal_simple(lua_State *);
         return 1; \
     }

-#define LUA_OBJECT_EXPORT_PROPERTY2(pfx, type, field, pusher, empty_value) \
+#define LUA_OBJECT_EXPORT_OPTIONAL_PROPERTY(pfx, type, field, pusher, empty_value) \
     static int \
     luaA_##pfx##_get_##field(lua_State *L, type *object) \
     { \
diff --git a/objects/client.c b/objects/client.c
index 01b40ec..4b9e85e 100644
--- a/objects/client.c
+++ b/objects/client.c
@@ -2770,16 +2770,16 @@ luaA_client_get_icon_name(lua_State *L, client_t *c)
     return 1;
 }

-LUA_OBJECT_EXPORT_PROPERTY2(client, client_t, screen, luaA_object_push, NULL)
+LUA_OBJECT_EXPORT_OPTIONAL_PROPERTY(client, client_t, screen, luaA_object_push, NULL)
 LUA_OBJECT_EXPORT_PROPERTY(client, client_t, class, lua_pushstring)
 LUA_OBJECT_EXPORT_PROPERTY(client, client_t, instance, lua_pushstring)
-LUA_OBJECT_EXPORT_PROPERTY2(client, client_t, machine, lua_pushstring, NULL)
+LUA_OBJECT_EXPORT_OPTIONAL_PROPERTY(client, client_t, machine, lua_pushstring, NULL)
 LUA_OBJECT_EXPORT_PROPERTY(client, client_t, role, lua_pushstring)
 LUA_OBJECT_EXPORT_PROPERTY(client, client_t, transient_for, luaA_object_push)
 LUA_OBJECT_EXPORT_PROPERTY(client, client_t, skip_taskbar, lua_pushboolean)
 LUA_OBJECT_EXPORT_PROPERTY(client, client_t, leader_window, lua_pushinteger)
 LUA_OBJECT_EXPORT_PROPERTY(client, client_t, group_window, lua_pushinteger)
-LUA_OBJECT_EXPORT_PROPERTY2(client, client_t, pid, lua_pushinteger, 0)
+LUA_OBJECT_EXPORT_OPTIONAL_PROPERTY(client, client_t, pid, lua_pushinteger, 0)
 LUA_OBJECT_EXPORT_PROPERTY(client, client_t, hidden, lua_pushboolean)
 LUA_OBJECT_EXPORT_PROPERTY(client, client_t, minimized, lua_pushboolean)
 LUA_OBJECT_EXPORT_PROPERTY(client, client_t, fullscreen, lua_pushboolean)