diff --git a/minix/kernel/mqueue.c b/minix/kernel/mqueue.c
index ff18f7c6f..efe38f334 100644
--- a/minix/kernel/mqueue.c
+++ b/minix/kernel/mqueue.c
@@ -43,10 +43,10 @@ int mq_open(const char *name, int oflag)
 	mqd_t mqd;
 
 	if (mq.num_queues == MAX_QUEUES)
-		return (mqd_t) -1;
+		return EMQUEUEFULL;
 
 	if (strlen(name) > NAME_SIZE)
-		return (mqd_t) -1;
+		return EINVAL;
 
 	for (int i = 0; i < MAX_QUEUES; i++)
 		if (mq.queue_slot_empty[i] == NOT_EMPTY)