Index: sys/kern/vfs_aio.c
===================================================================
--- sys/kern/vfs_aio.c
+++ sys/kern/vfs_aio.c
@@ -2489,8 +2489,11 @@
 
 	ops->store_aiocb(aiocbp, NULL);
 
-	timo = 0;
-	if (ts) {
+	if (ts == NULL) {
+		timo = 0;
+	} else if (ts->tv_sec == 0 && ts->tv_nsec == 0) {
+		timo = -1;
+	} else {
 		if ((ts->tv_nsec < 0) || (ts->tv_nsec >= 1000000000))
 			return (EINVAL);
 
@@ -2507,14 +2510,20 @@
 	error = 0;
 	cb = NULL;
 	AIO_LOCK(ki);
-	while ((cb = TAILQ_FIRST(&ki->kaio_done)) == NULL) {
-		ki->kaio_flags |= KAIO_WAKEUP;
-		error = msleep(&p->p_aioinfo, AIO_MTX(ki), PRIBIO | PCATCH,
-		    "aiowc", timo);
-		if (timo && error == ERESTART)
-			error = EINTR;
-		if (error)
-			break;
+	if (timo == -1) {
+		cb = TAILQ_FIRST(&ki->kaio_done);
+		if (cb == NULL)
+			error = EAGAIN;
+	} else {
+		while ((cb = TAILQ_FIRST(&ki->kaio_done)) == NULL) {
+			ki->kaio_flags |= KAIO_WAKEUP;
+			error = msleep(&p->p_aioinfo, AIO_MTX(ki),
+			    PRIBIO | PCATCH, "aiowc", timo);
+			if (timo && error == ERESTART)
+				error = EINTR;
+			if (error)
+				break;
+		}
 	}
 
 	if (cb != NULL) {