diff --git a/crates/luaffi_impl/src/metatype.rs b/crates/luaffi_impl/src/metatype.rs
index b63425b..ca2eb5c 100644
--- a/crates/luaffi_impl/src/metatype.rs
+++ b/crates/luaffi_impl/src/metatype.rs
@@ -745,11 +745,17 @@ fn inject_merged_drop(registry: &mut Registry, lua: Option<&LuaFunction>) -> Res
             "finaliser must take exactly one parameter"
         );
 
-        syn_assert!(
-            pat_ident(&lua.params[0])? == "self",
-            lua.params[0],
-            "finaliser parameter must be `self`"
-        );
+        match lua.params[0] {
+            // should be `self: cdata` PatType
+            Pat::Type(ref ty) => {
+                syn_assert!(
+                    pat_ident(&ty.pat)? == "self",
+                    lua.params[0],
+                    "finaliser parameter must be `self`"
+                );
+            }
+            _ => syn_error!(lua.params[0], "finaliser parameter must be `self`"),
+        }
 
         let params = &lua.params;
         let body = &lua.body;