diff --git a/client.c b/client.c
index 47342945c..a34be7d50 100644
--- a/client.c
+++ b/client.c
@@ -900,7 +900,7 @@ client_setborder(client_t *c, uint32_t width)
 static int
 luaA_client_border_set(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     uint32_t width = luaA_getopt_number(L, 2, "width", 0);
     const char *colorstr = luaA_getopt_string(L, 2, "color", NULL);
     xcolor_t color;
@@ -918,7 +918,7 @@ luaA_client_border_set(lua_State *L)
 static int
 luaA_client_screen_set(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     int screen = luaL_checknumber(L, 2) - 1;
     luaA_checkscreen(screen);
     move_client_to_screen(*c, screen, true);
@@ -928,7 +928,7 @@ luaA_client_screen_set(lua_State *L)
 static int
 luaA_client_screen_get(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     lua_pushnumber(L, 1 + (*c)->screen);
     return 1;
 }
@@ -937,8 +937,8 @@ luaA_client_screen_get(lua_State *L)
 static int
 luaA_client_tag(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
-    tag_t **tag = luaL_checkudata(L, 2, "tag");
+    client_t **c = luaA_checkudata(L, 1, "client");
+    tag_t **tag = luaA_checkudata(L, 2, "tag");
     bool tag_the_client = luaA_checkboolean(L, 3);
 
     if((*tag)->screen != (*c)->screen)
@@ -955,8 +955,8 @@ luaA_client_tag(lua_State *L)
 static int
 luaA_client_istagged(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
-    tag_t **tag = luaL_checkudata(L, 2, "tag");
+    client_t **c = luaA_checkudata(L, 1, "client");
+    tag_t **tag = luaA_checkudata(L, 2, "tag");
     lua_pushboolean(L, is_client_tagged(*c, *tag));
     return 1;
 }
@@ -964,7 +964,7 @@ luaA_client_istagged(lua_State *L)
 static int
 luaA_client_coords_get(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     lua_newtable(L);
     lua_pushnumber(L, (*c)->geometry.width);
     lua_setfield(L, -2, "width");
@@ -980,7 +980,7 @@ luaA_client_coords_get(lua_State *L)
 static int
 luaA_client_coords_set(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     area_t geometry;
 
     if((*c)->isfloating || layout_get_current((*c)->screen) == layout_floating)
@@ -999,7 +999,7 @@ luaA_client_coords_set(lua_State *L)
 static int
 luaA_client_opacity_set(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     double opacity = luaL_checknumber(L, 2);
 
     if(opacity == -1 || (opacity >= 0 && opacity <= 100))
@@ -1010,7 +1010,7 @@ luaA_client_opacity_set(lua_State *L)
 static int
 luaA_client_kill(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     client_kill(*c);
     return 0;
 }
@@ -1018,8 +1018,8 @@ luaA_client_kill(lua_State *L)
 static int
 luaA_client_swap(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
-    client_t **swap = luaL_checkudata(L, 2, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
+    client_t **swap = luaA_checkudata(L, 2, "client");
     client_list_swap(&globalconf.clients, *swap, *c);
     globalconf.screens[(*c)->screen].need_arrange = true;
     globalconf.screens[(*swap)->screen].need_arrange = true;
@@ -1031,7 +1031,7 @@ luaA_client_swap(lua_State *L)
 static int
 luaA_client_focus_set(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     client_focus(*c, (*c)->screen);
     return 0;
 }
@@ -1041,7 +1041,7 @@ luaA_client_focus_set(lua_State *L)
 static int
 luaA_client_raise(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     client_raise(*c);
     return 0;
 }
@@ -1049,7 +1049,7 @@ luaA_client_raise(lua_State *L)
 static int
 luaA_client_floating_set(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     bool f = luaA_checkboolean(L, 2);
     client_setfloating(*c, f, (*c)->layer == LAYER_FLOAT ? LAYER_TILE : LAYER_FLOAT);
     return 0;
@@ -1058,7 +1058,7 @@ luaA_client_floating_set(lua_State *L)
 static int
 luaA_client_floating_get(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     lua_pushboolean(L, (*c)->isfloating);
     return 1;
 }
@@ -1066,8 +1066,8 @@ luaA_client_floating_get(lua_State *L)
 static int
 luaA_client_eq(lua_State *L)
 {
-    client_t **c1 = luaL_checkudata(L, 1, "client");
-    client_t **c2 = luaL_checkudata(L, 2, "client");
+    client_t **c1 = luaA_checkudata(L, 1, "client");
+    client_t **c2 = luaA_checkudata(L, 2, "client");
     lua_pushboolean(L, (*c1 == *c2));
     return 1;
 }
@@ -1075,7 +1075,7 @@ luaA_client_eq(lua_State *L)
 static int
 luaA_client_redraw(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     xcb_unmap_window(globalconf.connection, (*c)->win);
     xcb_map_window(globalconf.connection, (*c)->win);
     return 0;
@@ -1084,7 +1084,7 @@ luaA_client_redraw(lua_State *L)
 static int
 luaA_client_tostring(lua_State *L)
 {
-    client_t **p = luaL_checkudata(L, 1, "client");
+    client_t **p = luaA_checkudata(L, 1, "client");
     lua_pushfstring(L, "[client udata(%p) name(%s)]", *p, (*p)->name);
     return 1;
 }
@@ -1092,7 +1092,7 @@ luaA_client_tostring(lua_State *L)
 static int
 luaA_client_icon_set(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     const char *icon = luaL_optstring(L, 2, NULL);
 
     p_delete(&(*c)->icon_path);
@@ -1107,7 +1107,7 @@ luaA_client_icon_set(lua_State *L)
 static int
 luaA_client_name_get(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     lua_pushstring(L, (*c)->name);
     return 1;
 }
@@ -1118,7 +1118,7 @@ luaA_client_name_get(lua_State *L)
 static int
 luaA_client_name_set(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     const char *name = luaL_checkstring(L, 2);
     p_delete(&(*c)->name);
     (*c)->name = a_strdup(name);
@@ -1131,8 +1131,8 @@ luaA_client_name_set(lua_State *L)
 static int
 luaA_client_titlebar_set(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
-    titlebar_t **t = luaL_checkudata(L, 2, "titlebar");
+    client_t **c = luaA_checkudata(L, 1, "client");
+    titlebar_t **t = luaA_checkudata(L, 2, "titlebar");
 
     if(client_getbytitlebar(*t))
         luaL_error(L, "titlebar is already used by another client");
@@ -1160,7 +1160,7 @@ luaA_client_titlebar_set(lua_State *L)
 static int
 luaA_client_titlebar_get(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
 
     if((*c)->titlebar)
         return luaA_titlebar_userdata_new((*c)->titlebar);
@@ -1173,7 +1173,7 @@ luaA_client_titlebar_get(lua_State *L)
 static int
 luaA_client_unmanage(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     client_unmanage(*c);
     return 0;
 }
diff --git a/keybinding.c b/keybinding.c
index 177637c42..4de5a98e3 100644
--- a/keybinding.c
+++ b/keybinding.c
@@ -88,7 +88,7 @@ luaA_keybinding_new(lua_State *L)
 static int
 luaA_keybinding_add(lua_State *L)
 {
-    keybinding_t *key, **k = luaL_checkudata(L, 1, "keybinding");
+    keybinding_t *key, **k = luaA_checkudata(L, 1, "keybinding");
 
     /* Check that the keybinding has not been already added. */
     for(key = globalconf.keys; key; key = key->next)
@@ -109,7 +109,7 @@ luaA_keybinding_add(lua_State *L)
 static int
 luaA_keybinding_remove(lua_State *L)
 {
-    keybinding_t **k = luaL_checkudata(L, 1, "keybinding");
+    keybinding_t **k = luaA_checkudata(L, 1, "keybinding");
 
     keybinding_list_detach(&globalconf.keys, *k);
 
@@ -125,7 +125,7 @@ luaA_keybinding_remove(lua_State *L)
 static int
 luaA_keybinding_gc(lua_State *L)
 {
-    keybinding_t **keybinding = luaL_checkudata(L, 1, "keybinding");
+    keybinding_t **keybinding = luaA_checkudata(L, 1, "keybinding");
     keybinding_unref(keybinding);
     keybinding = NULL;
     return 0;
@@ -137,7 +137,7 @@ luaA_keybinding_gc(lua_State *L)
 static int
 luaA_keybinding_tostring(lua_State *L)
 {
-    keybinding_t **p = luaL_checkudata(L, 1, "keybinding");
+    keybinding_t **p = luaA_checkudata(L, 1, "keybinding");
     lua_pushfstring(L, "[keybinding udata(%p)]", *p);
     return 1;
 }
diff --git a/lua.h b/lua.h
index 80ed8f5af..e37cc107e 100644
--- a/lua.h
+++ b/lua.h
@@ -69,6 +69,22 @@ typedef int luaA_function;
             luaL_error(L, "invalid screen number: %d\n", screen); \
     } while(0)
 
+/** Check that an object is not a NULL reference.
+ * \param L The Lua state.
+ * \param ud The index of the object in the stack.
+ * \param tname The type name.
+ * \return A pointer to the object.
+ */
+static inline void *
+luaA_checkudata(lua_State *L, int ud, const char *tname)
+{
+    void **p = luaL_checkudata(L, ud, tname);
+    if(*p)
+        return p;
+    luaL_error(L, "invalid object");
+    return NULL;
+}
+
 static inline lua_Number
 luaA_getopt_number(lua_State *L, int idx, const char *name, lua_Number def)
 {
diff --git a/mouse.c b/mouse.c
index 43e6835a7..90125f08d 100644
--- a/mouse.c
+++ b/mouse.c
@@ -476,7 +476,7 @@ luaA_mouse_coords_set(lua_State *L)
 int
 luaA_client_mouse_resize(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     mouse_client_resize(*c);
     return 0;
 }
@@ -487,7 +487,7 @@ luaA_client_mouse_resize(lua_State *L)
 int
 luaA_client_mouse_move(lua_State *L)
 {
-    client_t **c = luaL_checkudata(L, 1, "client");
+    client_t **c = luaA_checkudata(L, 1, "client");
     int snap = luaL_optnumber(L, 2, 8);
     mouse_client_move(*c, snap);
     return 0;
diff --git a/statusbar.c b/statusbar.c
index d35a83046..84af50cec 100644
--- a/statusbar.c
+++ b/statusbar.c
@@ -282,8 +282,8 @@ statusbar_position_update(statusbar_t *statusbar, position_t position)
 static int
 luaA_statusbar_eq(lua_State *L)
 {
-    statusbar_t **t1 = luaL_checkudata(L, 1, "statusbar");
-    statusbar_t **t2 = luaL_checkudata(L, 2, "statusbar");
+    statusbar_t **t1 = luaA_checkudata(L, 1, "statusbar");
+    statusbar_t **t2 = luaA_checkudata(L, 2, "statusbar");
     lua_pushboolean(L, (*t1 == *t2));
     return 1;
 }
@@ -294,7 +294,7 @@ luaA_statusbar_eq(lua_State *L)
 static int
 luaA_statusbar_position_set(lua_State *L)
 {
-    statusbar_t *s, **sb = luaL_checkudata(L, 1, "statusbar");
+    statusbar_t *s, **sb = luaA_checkudata(L, 1, "statusbar");
     const char *pos = luaL_checkstring(L, 2);
     position_t position = position_get_from_str(pos);
 
@@ -314,7 +314,7 @@ luaA_statusbar_position_set(lua_State *L)
 static int
 luaA_statusbar_position_get(lua_State *L)
 {
-    statusbar_t **sb = luaL_checkudata(L, 1, "statusbar");
+    statusbar_t **sb = luaA_checkudata(L, 1, "statusbar");
     lua_pushstring(L, position_to_str((*sb)->position));
     return 1;
 }
@@ -325,7 +325,7 @@ luaA_statusbar_position_get(lua_State *L)
 static int
 luaA_statusbar_align_set(lua_State *L)
 {
-    statusbar_t **sb = luaL_checkudata(L, 1, "statusbar");
+    statusbar_t **sb = luaA_checkudata(L, 1, "statusbar");
     const char *al = luaL_checkstring(L, 2);
     alignment_t align = draw_align_get_from_str(al);
 
@@ -340,7 +340,7 @@ luaA_statusbar_align_set(lua_State *L)
 static int
 luaA_statusbar_tostring(lua_State *L)
 {
-    statusbar_t **p = luaL_checkudata(L, 1, "statusbar");
+    statusbar_t **p = luaA_checkudata(L, 1, "statusbar");
     lua_pushfstring(L, "[statusbar udata(%p) name(%s)]", *p, (*p)->name);
     return 1;
 }
@@ -351,8 +351,8 @@ luaA_statusbar_tostring(lua_State *L)
 static int
 luaA_statusbar_widget_add(lua_State *L)
 {
-    statusbar_t **sb = luaL_checkudata(L, 1, "statusbar");
-    widget_t **widget = luaL_checkudata(L, 2, "widget");
+    statusbar_t **sb = luaA_checkudata(L, 1, "statusbar");
+    widget_t **widget = luaA_checkudata(L, 2, "widget");
     widget_node_t *w = p_new(widget_node_t, 1);
 
     (*sb)->need_update = true;
@@ -369,7 +369,7 @@ luaA_statusbar_widget_add(lua_State *L)
 static int
 luaA_statusbar_add(lua_State *L)
 {
-    statusbar_t *s, **sb = luaL_checkudata(L, 1, "statusbar");
+    statusbar_t *s, **sb = luaA_checkudata(L, 1, "statusbar");
     int i, screen = luaL_checknumber(L, 2) - 1;
 
     luaA_checkscreen(screen);
@@ -404,7 +404,7 @@ luaA_statusbar_add(lua_State *L)
 static int
 luaA_statusbar_remove(lua_State *L)
 {
-    statusbar_t *s, **sb = luaL_checkudata(L, 1, "statusbar");
+    statusbar_t *s, **sb = luaA_checkudata(L, 1, "statusbar");
     int i;
 
     for(i = 0; i < globalconf.screens_info->nscreen; i++)
@@ -479,7 +479,7 @@ luaA_statusbar_new(lua_State *L)
 static int
 luaA_statusbar_widget_get(lua_State *L)
 {
-    statusbar_t **sb = luaL_checkudata(L, 1, "statusbar");
+    statusbar_t **sb = luaA_checkudata(L, 1, "statusbar");
     widget_node_t *widget;
     int i = 1;
 
@@ -501,7 +501,7 @@ luaA_statusbar_widget_get(lua_State *L)
 static int
 luaA_statusbar_gc(lua_State *L)
 {
-    statusbar_t **sb = luaL_checkudata(L, 1, "statusbar");
+    statusbar_t **sb = luaA_checkudata(L, 1, "statusbar");
     statusbar_unref(sb);
     *sb = NULL;
     return 0;
diff --git a/tag.c b/tag.c
index 2ed136bf0..5550f41b0 100644
--- a/tag.c
+++ b/tag.c
@@ -242,8 +242,8 @@ tag_view_only_byindex(int screen, int dindex)
 static int
 luaA_tag_eq(lua_State *L)
 {
-    tag_t **t1 = luaL_checkudata(L, 1, "tag");
-    tag_t **t2 = luaL_checkudata(L, 2, "tag");
+    tag_t **t1 = luaA_checkudata(L, 1, "tag");
+    tag_t **t2 = luaA_checkudata(L, 2, "tag");
     lua_pushboolean(L, (*t1 == *t2));
     return 1;
 }
@@ -254,7 +254,7 @@ luaA_tag_eq(lua_State *L)
 static int
 luaA_tag_tostring(lua_State *L)
 {
-    tag_t **p = luaL_checkudata(L, 1, "tag");
+    tag_t **p = luaA_checkudata(L, 1, "tag");
     lua_pushfstring(L, "[tag udata(%p) name(%s)]", *p, (*p)->name);
     return 1;
 }
@@ -265,7 +265,7 @@ luaA_tag_tostring(lua_State *L)
 static int
 luaA_tag_add(lua_State *L)
 {
-    tag_t *t, **tag = luaL_checkudata(L, 1, "tag");
+    tag_t *t, **tag = luaA_checkudata(L, 1, "tag");
     int i, screen = luaL_checknumber(L, 2) - 1;
     luaA_checkscreen(screen);
 
@@ -340,7 +340,7 @@ luaA_tag_new(lua_State *L)
 static int
 luaA_tag_view(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     bool view = luaA_checkboolean(L, 2);
     tag_view(*tag, view);
     return 0;
@@ -352,7 +352,7 @@ luaA_tag_view(lua_State *L)
 static int
 luaA_tag_isselected(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     lua_pushboolean(L, (*tag)->selected);
     return 1;
 }
@@ -364,7 +364,7 @@ luaA_tag_isselected(lua_State *L)
 static int
 luaA_tag_mwfact_set(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     double mwfact = luaL_checknumber(L, 2);
 
     if(mwfact < 1 && mwfact > 0)
@@ -384,7 +384,7 @@ luaA_tag_mwfact_set(lua_State *L)
 static int
 luaA_tag_mwfact_get(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     lua_pushnumber(L, (*tag)->mwfact);
     return 1;
 }
@@ -396,7 +396,7 @@ luaA_tag_mwfact_get(lua_State *L)
 static int
 luaA_tag_ncol_set(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     int ncol = luaL_checknumber(L, 2);
 
     if(ncol >= 1)
@@ -416,7 +416,7 @@ luaA_tag_ncol_set(lua_State *L)
 static int
 luaA_tag_ncol_get(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     lua_pushnumber(L, (*tag)->ncol);
     return 1;
 }
@@ -428,7 +428,7 @@ luaA_tag_ncol_get(lua_State *L)
 static int
 luaA_tag_nmaster_set(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     int nmaster = luaL_checknumber(L, 2);
 
     if(nmaster >= 0)
@@ -448,7 +448,7 @@ luaA_tag_nmaster_set(lua_State *L)
 static int
 luaA_tag_nmaster_get(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     lua_pushnumber(L, (*tag)->nmaster);
     return 1;
 }
@@ -459,7 +459,7 @@ luaA_tag_nmaster_get(lua_State *L)
 static int
 luaA_tag_name_get(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     lua_pushstring(L, (*tag)->name);
     return 1;
 }
@@ -470,7 +470,7 @@ luaA_tag_name_get(lua_State *L)
 static int
 luaA_tag_name_set(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     const char *name = luaL_checkstring(L, 2);
     p_delete(&(*tag)->name);
     (*tag)->name = a_strdup(name);
@@ -482,7 +482,7 @@ luaA_tag_name_set(lua_State *L)
 static int
 luaA_tag_gc(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     tag_unref(tag);
     *tag = NULL;
     return 0;
@@ -494,7 +494,7 @@ luaA_tag_gc(lua_State *L)
 static int
 luaA_tag_layout_get(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     const char *name = a_strdup(name_func_rlookup((*tag)->layout, LayoutList));
     lua_pushstring(L, name);
     return 1;
@@ -506,7 +506,7 @@ luaA_tag_layout_get(lua_State *L)
 static int
 luaA_tag_layout_set(lua_State *L)
 {
-    tag_t **tag = luaL_checkudata(L, 1, "tag");
+    tag_t **tag = luaA_checkudata(L, 1, "tag");
     const char *name = luaL_checkstring(L, 2);
     layout_t *l = name_func_lookup(name, LayoutList);
 
diff --git a/titlebar.c b/titlebar.c
index 011b1288c..ff2ab574a 100644
--- a/titlebar.c
+++ b/titlebar.c
@@ -452,8 +452,8 @@ luaA_titlebar_new(lua_State *L)
 static int
 luaA_titlebar_widget_add(lua_State *L)
 {
-    titlebar_t **tb = luaL_checkudata(L, 1, "titlebar");
-    widget_t **widget = luaL_checkudata(L, 2, "widget");
+    titlebar_t **tb = luaA_checkudata(L, 1, "titlebar");
+    widget_t **widget = luaA_checkudata(L, 2, "widget");
     widget_node_t *w = p_new(widget_node_t, 1);
     client_t *c;
 
@@ -477,7 +477,7 @@ luaA_titlebar_widget_add(lua_State *L)
 static int
 luaA_titlebar_widget_get(lua_State *L)
 {
-    titlebar_t **tb = luaL_checkudata(L, 1, "titlebar");
+    titlebar_t **tb = luaA_checkudata(L, 1, "titlebar");
     widget_node_t *widget;
     int i = 1;
 
@@ -501,7 +501,7 @@ luaA_titlebar_widget_get(lua_State *L)
 static int
 luaA_titlebar_client_get(lua_State *L)
 {
-    titlebar_t **titlebar = luaL_checkudata(L, 1, "titlebar");
+    titlebar_t **titlebar = luaA_checkudata(L, 1, "titlebar");
     client_t *c;
 
     if((c = client_getbytitlebar(*titlebar)))
@@ -525,7 +525,7 @@ luaA_titlebar_userdata_new(titlebar_t *t)
 static int
 luaA_titlebar_gc(lua_State *L)
 {
-    titlebar_t **titlebar = luaL_checkudata(L, 1, "titlebar");
+    titlebar_t **titlebar = luaA_checkudata(L, 1, "titlebar");
     titlebar_unref(titlebar);
     *titlebar = NULL;
     return 0;
@@ -534,7 +534,7 @@ luaA_titlebar_gc(lua_State *L)
 static int
 luaA_titlebar_tostring(lua_State *L)
 {
-    titlebar_t **p = luaL_checkudata(L, 1, "titlebar");
+    titlebar_t **p = luaA_checkudata(L, 1, "titlebar");
     lua_pushfstring(L, "[titlebar udata(%p)]", *p);
     return 1;
 }
@@ -542,8 +542,8 @@ luaA_titlebar_tostring(lua_State *L)
 static int
 luaA_titlebar_eq(lua_State *L)
 {
-    titlebar_t **t1 = luaL_checkudata(L, 1, "titlebar");
-    titlebar_t **t2 = luaL_checkudata(L, 2, "titlebar");
+    titlebar_t **t1 = luaA_checkudata(L, 1, "titlebar");
+    titlebar_t **t2 = luaA_checkudata(L, 2, "titlebar");
     lua_pushboolean(L, (*t1 == *t2));
     return 1;
 }
diff --git a/widget.c b/widget.c
index ad21f5583..1739b14c4 100644
--- a/widget.c
+++ b/widget.c
@@ -347,7 +347,7 @@ luaA_widget_mouse(lua_State *L)
 {
     size_t i, len;
     /* arg 1 is object */
-    widget_t **widget = luaL_checkudata(L, 1, "widget");
+    widget_t **widget = luaA_checkudata(L, 1, "widget");
     int b;
     button_t *button;
 
@@ -419,7 +419,7 @@ widget_tell_managestatus(widget_t *widget, widget_tell_status_t status, const ch
 static int
 luaA_widget_set(lua_State *L)
 {
-    widget_t **widget = luaL_checkudata(L, 1, "widget");
+    widget_t **widget = luaA_checkudata(L, 1, "widget");
     const char *property, *value;
     widget_tell_status_t status;
 
@@ -436,7 +436,7 @@ luaA_widget_set(lua_State *L)
 static int
 luaA_widget_gc(lua_State *L)
 {
-    widget_t **widget = luaL_checkudata(L, 1, "widget");
+    widget_t **widget = luaA_checkudata(L, 1, "widget");
     widget_unref(widget);
     *widget = NULL;
     return 0;
@@ -447,7 +447,7 @@ luaA_widget_gc(lua_State *L)
 static int
 luaA_widget_tostring(lua_State *L)
 {
-    widget_t **p = luaL_checkudata(L, 1, "widget");
+    widget_t **p = luaA_checkudata(L, 1, "widget");
     lua_pushfstring(L, "[widget udata(%p) name(%s)]", *p, (*p)->name);
     return 1;
 }
@@ -458,8 +458,8 @@ luaA_widget_tostring(lua_State *L)
 static int
 luaA_widget_eq(lua_State *L)
 {
-    widget_t **t1 = luaL_checkudata(L, 1, "widget");
-    widget_t **t2 = luaL_checkudata(L, 2, "widget");
+    widget_t **t1 = luaA_checkudata(L, 1, "widget");
+    widget_t **t2 = luaA_checkudata(L, 2, "widget");
     lua_pushboolean(L, (*t1 == *t2));
     return 1;
 }
@@ -470,7 +470,7 @@ luaA_widget_eq(lua_State *L)
 static int
 luaA_widget_name_set(lua_State *L)
 {
-    widget_t **widget = luaL_checkudata(L, 1, "widget");
+    widget_t **widget = luaA_checkudata(L, 1, "widget");
     const char *name = luaL_checkstring(L, 2);
     p_delete(&(*widget)->name);
     (*widget)->name = a_strdup(name);
@@ -483,7 +483,7 @@ luaA_widget_name_set(lua_State *L)
 static int
 luaA_widget_name_get(lua_State *L)
 {
-    widget_t **widget = luaL_checkudata(L, 1, "widget");
+    widget_t **widget = luaA_checkudata(L, 1, "widget");
     lua_pushstring(L, (*widget)->name);
     return 1;
 }
@@ -495,7 +495,7 @@ luaA_widget_name_get(lua_State *L)
 static int
 luaA_widget_visible_set(lua_State *L)
 {
-    widget_t **widget = luaL_checkudata(L, 1, "widget");
+    widget_t **widget = luaA_checkudata(L, 1, "widget");
     (*widget)->isvisible = luaA_checkboolean(L, 2);
     widget_invalidate_bywidget(*widget);
     return 0;
@@ -507,7 +507,7 @@ luaA_widget_visible_set(lua_State *L)
 static int
 luaA_widget_visible_get(lua_State *L)
 {
-    widget_t **widget = luaL_checkudata(L, 1, "widget");
+    widget_t **widget = luaA_checkudata(L, 1, "widget");
     lua_pushboolean(L, (*widget)->isvisible);
     return 1;
 }