diff --git a/include/luak/luak.h b/include/luak/luak.h
index 0918d8b..7559701 100644
--- a/include/luak/luak.h
+++ b/include/luak/luak.h
@@ -19,6 +19,7 @@ struct kiwmi_lua {
     struct wl_list callbacks; // lua_callback::link
 };
 
+int luaK_callback_register_dispatch(lua_State *L);
 struct kiwmi_lua *luaK_create(struct kiwmi_server *server);
 bool luaK_dofile(struct kiwmi_lua *lua, const char *config_path);
 void luaK_destroy(struct kiwmi_lua *lua);
diff --git a/kiwmi/luak/kiwmi_server.c b/kiwmi/luak/kiwmi_server.c
index c2709da..6608a0e 100644
--- a/kiwmi/luak/kiwmi_server.c
+++ b/kiwmi/luak/kiwmi_server.c
@@ -18,30 +18,6 @@
 #include "luak/kiwmi_view.h"
 #include "server.h"
 
-static int
-l_kiwmi_server_on(lua_State *L)
-{
-    luaL_checkudata(L, 1, "kiwmi_server"); // server
-    luaL_checktype(L, 2, LUA_TSTRING);     // type
-    luaL_checktype(L, 3, LUA_TFUNCTION);   // callback
-
-    lua_getmetatable(L, 1);
-    lua_getfield(L, -1, "__events");
-    lua_pushvalue(L, 2);
-    lua_gettable(L, -2);
-
-    luaL_argcheck(L, lua_iscfunction(L, -1), 2, "invalid event");
-    lua_pushvalue(L, 1);
-    lua_pushvalue(L, 3);
-
-    if (lua_pcall(L, 2, 1, 0)) {
-        wlr_log(WLR_ERROR, "%s", lua_tostring(L, -1));
-        return 0;
-    }
-
-    return 1;
-}
-
 static int
 l_kiwmi_server_quit(lua_State *L)
 {
@@ -88,7 +64,7 @@ l_kiwmi_server_view_under_cursor(lua_State *L)
 }
 
 static const luaL_Reg kiwmi_server_methods[] = {
-    {"on", l_kiwmi_server_on},
+    {"on", luaK_callback_register_dispatch},
     {"quit", l_kiwmi_server_quit},
     {"view_under_cursor", l_kiwmi_server_view_under_cursor},
     {NULL, NULL},
diff --git a/kiwmi/luak/luak.c b/kiwmi/luak/luak.c
index e14b7fb..66822f5 100644
--- a/kiwmi/luak/luak.c
+++ b/kiwmi/luak/luak.c
@@ -17,6 +17,32 @@
 #include "luak/kiwmi_server.h"
 #include "luak/kiwmi_view.h"
 
+int
+luaK_callback_register_dispatch(lua_State *L)
+{
+    luaL_checktype(L, 1, LUA_TUSERDATA); // server
+    luaL_checktype(L, 2, LUA_TSTRING);   // type
+    luaL_checktype(L, 3, LUA_TFUNCTION); // callback
+
+    int has_mt = lua_getmetatable(L, 1);
+    luaL_argcheck(L, has_mt, 1, "no metatable");
+    lua_getfield(L, -1, "__events");
+    luaL_argcheck(L, lua_istable(L, -1), 1, "no __events");
+    lua_pushvalue(L, 2);
+    lua_gettable(L, -2);
+
+    luaL_argcheck(L, lua_iscfunction(L, -1), 2, "invalid event");
+    lua_pushvalue(L, 1);
+    lua_pushvalue(L, 3);
+
+    if (lua_pcall(L, 2, 1, 0)) {
+        wlr_log(WLR_ERROR, "%s", lua_tostring(L, -1));
+        return 0;
+    }
+
+    return 1;
+}
+
 struct kiwmi_lua *
 luaK_create(struct kiwmi_server *server)
 {