diff --git a/include/villas/queue.h b/include/villas/queue.h
index 30e29b64b..50e850260 100644
--- a/include/villas/queue.h
+++ b/include/villas/queue.h
@@ -56,7 +56,7 @@ struct queue_cell {
 struct queue {
 	cacheline_pad_t _pad0;	/**< Shared area: all threads read */
 
-	atomic_size_t state;
+	_Atomic enum state state;
 
 	struct memtype *mem;
 	size_t buffer_mask;
diff --git a/lib/queue.c b/lib/queue.c
index a10d9c360..2ca6c86c1 100644
--- a/lib/queue.c
+++ b/lib/queue.c
@@ -188,8 +188,8 @@ int queue_pull_many(struct queue *q, void *ptr[], size_t cnt)
 
 int queue_close(struct queue *q)
 {
-	size_t expected = STATE_INITIALIZED;
-	if (atomic_compare_exchange_weak_explicit(&q->state, &expected, STATE_STOPPED, memory_order_relaxed, memory_order_relaxed)) {
+	enum state expected = STATE_INITIALIZED;
+	if (atomic_compare_exchange_weak_explicit(&q->state, &expected, STATE_STOPPED, memory_order_relaxed, memory_order_relaxed))
 		return 0;
 
 	return -1;