diff --git a/src/async/async.c b/src/async/async.c
index d78375478..0c17504e4 100644
--- a/src/async/async.c
+++ b/src/async/async.c
@@ -18,6 +18,7 @@
 
 struct async_work {
 	struct le le;
+	mtx_t *mtx;
 	re_async_work_h *workh;
 	re_async_h *cb;
 	void *arg;
@@ -66,8 +67,10 @@ static int worker_thread(void *arg)
 		mtx_unlock(&a->mtx);
 
 		work = le->data;
+		mtx_lock(work->mtx);
 		if (work->workh)
 			work->err = work->workh(work->arg);
+		mtx_unlock(work->mtx);
 
 		mtx_lock(&a->mtx);
 		mqueue_push(a->mqueue, 0, work);
@@ -127,8 +130,10 @@ static void queueh(int id, void *data, void *arg)
 	struct re_async *async	= arg;
 	(void)id;
 
+	mtx_lock(work->mtx);
 	if (work->cb)
 		work->cb(work->err, work->arg);
+	mtx_unlock(work->mtx);
 
 	mtx_lock(&async->mtx);
 	list_move(&work->le, &async->freel);
@@ -136,6 +141,38 @@ static void queueh(int id, void *data, void *arg)
 }
 
 
+static void work_destruct(void *arg)
+{
+	struct async_work *work = arg;
+	mem_deref(work->mtx);
+}
+
+
+static int work_alloc(struct async_work **workp)
+{
+	int err;
+	struct async_work *work;
+
+	work = mem_zalloc(sizeof(struct async_work), NULL);
+	if (!work) {
+		err = ENOMEM;
+		return err;
+	}
+
+	err = mutex_alloc(&work->mtx);
+	if (err) {
+		mem_deref(work);
+		return err;
+	}
+
+	mem_destructor(work, work_destruct);
+
+	*workp = work;
+
+	return 0;
+}
+
+
 /**
  * Allocate a new async object
  *
@@ -148,7 +185,7 @@ int re_async_alloc(struct re_async **asyncp, uint16_t workers)
 {
 	int err;
 	struct re_async *async;
-	struct async_work *async_work;
+	struct async_work *work;
 
 	if (!asyncp || !workers)
 		return EINVAL;
@@ -186,13 +223,11 @@ int re_async_alloc(struct re_async **asyncp, uint16_t workers)
 		async->workers++;
 
 		/* preallocate */
-		async_work = mem_zalloc(sizeof(struct async_work), NULL);
-		if (!async_work) {
-			err = ENOMEM;
+		err = work_alloc(&work);
+		if (err)
 			goto err;
-		}
 
-		list_append(&async->freel, &async_work->le, async_work);
+		list_append(&async->freel, &work->le, work);
 	}
 
 	tmr_start(&async->tmr, 10, worker_check, async);
@@ -222,30 +257,29 @@ int re_async(struct re_async *async, intptr_t id, re_async_work_h *workh,
 	     re_async_h *cb, void *arg)
 {
 	int err = 0;
-	struct async_work *async_work;
+	struct async_work *work;
 
 	if (unlikely(!async))
 		return EINVAL;
 
 	mtx_lock(&async->mtx);
 	if (unlikely(list_isempty(&async->freel))) {
-		async_work = mem_zalloc(sizeof(struct async_work), NULL);
-		if (!async_work) {
-			err = ENOMEM;
+
+		err = work_alloc(&work);
+		if (err)
 			goto out;
-		}
 	}
 	else {
-		async_work = list_head(&async->freel)->data;
-		list_unlink(&async_work->le);
+		work = list_head(&async->freel)->data;
+		list_unlink(&work->le);
 	}
 
-	async_work->workh = workh;
-	async_work->cb	  = cb;
-	async_work->arg	  = arg;
-	async_work->id	  = id;
+	work->workh = workh;
+	work->cb    = cb;
+	work->arg   = arg;
+	work->id    = id;
 
-	list_append(&async->workl, &async_work->le, async_work);
+	list_append(&async->workl, &work->le, work);
 	cnd_signal(&async->wait);
 
 out:
@@ -279,11 +313,13 @@ void re_async_cancel(struct re_async *async, intptr_t id)
 		if (w->id != id)
 			continue;
 
+		mtx_lock(w->mtx);
 		w->id	 = 0;
 		w->workh = NULL;
 		w->cb	 = NULL;
 		w->arg	 = mem_deref(w->arg);
 		list_move(&w->le, &async->freel);
+		mtx_unlock(w->mtx);
 	}
 
 	le = list_head(&async->curl);
@@ -295,11 +331,13 @@ void re_async_cancel(struct re_async *async, intptr_t id)
 		if (w->id != id)
 			continue;
 
+		mtx_lock(w->mtx);
 		w->id	 = 0;
 		w->workh = NULL;
 		w->cb	 = NULL;
 		w->arg	 = mem_deref(w->arg);
 		list_move(&w->le, &async->freel);
+		mtx_unlock(w->mtx);
 	}
 
 	mtx_unlock(&async->mtx);