diff --git a/src/codegen/function_body_chunk.rs b/src/codegen/function_body_chunk.rs
index 36aee750a..442d83dff 100644
--- a/src/codegen/function_body_chunk.rs
+++ b/src/codegen/function_body_chunk.rs
@@ -242,11 +242,15 @@ impl Builder {
             Param { name: "res".to_string(), typ: format!("*mut {}::GAsyncResult", gio_crate_name) },
             Param { name: "user_data".to_string(), typ: format!("{}::gpointer", glib_crate_name) },
         ];
+        let body = Chunk::Chunks(vec![
+            Chunk::Custom("callback_guard!();".into()),
+            Chunk::Chunks(body),
+        ]);
 
         chunks.push(Chunk::ExternCFunc {
             name: format!("{}<{}: {}>", trampoline.name, trampoline.bound_name, trampoline.callback_type),
             parameters,
-            body: Box::new(Chunk::Chunks(body)),
+            body: Box::new(body),
         });
         let chunk = Chunk::Let {
             name: "callback".to_string(),
diff --git a/src/codegen/trampoline.rs b/src/codegen/trampoline.rs
index 743399427..ed22a4523 100644
--- a/src/codegen/trampoline.rs
+++ b/src/codegen/trampoline.rs
@@ -51,6 +51,7 @@ pub fn generate(
             object_name
         ));
     }
+    try!(writeln!(w, "\tcallback_guard!();"));
     try!(writeln!(w, "\tlet f: &&({}) = transmute(f);", func_str));
     try!(transformation_vars(w, analysis));
     let call = trampoline_call_func(env, analysis, in_trait);