diff --git a/mlua-sys/Cargo.toml b/mlua-sys/Cargo.toml
index 44f64df..4c6b78a 100644
--- a/mlua-sys/Cargo.toml
+++ b/mlua-sys/Cargo.toml
@@ -37,4 +37,4 @@ cfg-if = "1.0"
 pkg-config = "0.3.17"
 lua-src = { version = ">= 544.0.0, < 550.0.0", optional = true }
 luajit-src = { version = ">= 210.4.0, < 220.0.0", optional = true }
-luau0-src = { version = "0.5.0", optional = true }
+luau0-src = { version = "0.5.6", optional = true }
diff --git a/mlua-sys/src/luau/lua.rs b/mlua-sys/src/luau/lua.rs
index 22391ef..9556a4f 100644
--- a/mlua-sys/src/luau/lua.rs
+++ b/mlua-sys/src/luau/lua.rs
@@ -74,6 +74,7 @@ pub type lua_Continuation = unsafe extern "C" fn(L: *mut lua_State, status: c_in
 
 /// Type for userdata destructor functions.
 pub type lua_Udestructor = unsafe extern "C" fn(*mut c_void);
+pub type lua_Destructor = unsafe extern "C" fn(L: *mut lua_State, *mut c_void);
 
 /// Type for memory-allocation functions.
 pub type lua_Alloc = unsafe extern "C" fn(
@@ -265,11 +266,8 @@ extern "C" {
     // TODO: lua_encodepointer
     pub fn lua_clock() -> c_double;
     pub fn lua_setuserdatatag(L: *mut lua_State, idx: c_int, tag: c_int);
-    pub fn lua_setuserdatadtor(
-        L: *mut lua_State,
-        tag: c_int,
-        dtor: Option<unsafe extern "C" fn(*mut lua_State, *mut c_void)>,
-    );
+    pub fn lua_setuserdatadtor(L: *mut lua_State, tag: c_int, dtor: Option<lua_Destructor>);
+    pub fn lua_getuserdatadtor(L: *mut lua_State, tag: c_int) -> Option<lua_Destructor>;
     pub fn lua_clonefunction(L: *mut lua_State, idx: c_int);
     pub fn lua_cleartable(L: *mut lua_State, idx: c_int);
 }