diff --git a/common/luaobject.h b/common/luaobject.h
index c26af6fc5..c3e1f0560 100644
--- a/common/luaobject.h
+++ b/common/luaobject.h
@@ -195,6 +195,16 @@ int luaA_object_emit_signal_simple(lua_State *);
         return 1; \
     }
 
+#define LUA_OBJECT_EXPORT_OPTIONAL_PROPERTY(pfx, type, field, pusher, empty_value) \
+    static int \
+    luaA_##pfx##_get_##field(lua_State *L, type *object) \
+    { \
+        if (object->field == empty_value) \
+            return 0; \
+        pusher(L, object->field); \
+        return 1; \
+    }
+
 int luaA_object_tostring(lua_State *);
 
 #define LUA_OBJECT_META(prefix) \
diff --git a/objects/client.c b/objects/client.c
index 45ba08306..69f5be809 100644
--- a/objects/client.c
+++ b/objects/client.c
@@ -2770,15 +2770,16 @@ luaA_client_get_icon_name(lua_State *L, client_t *c)
     return 1;
 }
 
+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_PROPERTY(client, client_t, machine, lua_pushstring)
+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_PROPERTY(client, client_t, pid, lua_pushinteger)
+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)
@@ -2819,15 +2820,6 @@ luaA_client_get_content(lua_State *L, client_t *c)
     return 1;
 }
 
-static int
-luaA_client_get_screen(lua_State *L, client_t *c)
-{
-    if(!c->screen)
-        return 0;
-    luaA_object_push(L, c->screen);
-    return 1;
-}
-
 static int
 luaA_client_get_icon(lua_State *L, client_t *c)
 {