diff --git a/sys/dev/misc/snp/snp.c b/sys/dev/misc/snp/snp.c
index 1d83373..2a0a1cd 100644
--- a/sys/dev/misc/snp/snp.c
+++ b/sys/dev/misc/snp/snp.c
@@ -590,6 +590,9 @@ snpioctl(struct dev_ioctl_args *ap)
 			snp->snp_flags &= ~SNOOP_ASYNC;
 		break;
 
+	case FIONBIO:
+		break;
+
 	case FIONREAD:
 		crit_enter();
 		if (snp->snp_tty != NULL)
diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 9eebfe0..9056339 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -297,6 +297,11 @@ kern_fcntl(int fd, int cmd, union fcntl_dat *dat, struct ucred *cred)
 			error = fo_ioctl(fp, FIOASYNC, (caddr_t)&tmp,
 					 cred, NULL);
 		}
+		if (error == 0 && ((nflags ^ oflags) & FNONBLOCK)) {
+			tmp = nflags & FNONBLOCK;
+			error = fo_ioctl(fp, FIONBIO, (caddr_t)&tmp,
+					 cred, NULL);
+		}
 		if (error == 0)
 			fp->f_flag = nflags;
 		break;
diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
index 2a4829d..ddecb16 100644
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -1346,6 +1346,9 @@ kqueue_ioctl(struct file *fp, u_long com, caddr_t data,
 	lwkt_gettoken(tok);
 
 	switch(com) {
+	case FIONBIO:
+		error = 0;
+		break;
 	case FIOASYNC:
 		if (*(int *)data)
 			kq->kq_state |= KQ_ASYNC;
diff --git a/sys/kern/kern_memio.c b/sys/kern/kern_memio.c
index 5ead6fd..2a989ab 100644
--- a/sys/kern/kern_memio.c
+++ b/sys/kern/kern_memio.c
@@ -572,6 +572,8 @@ random_ioctl(cdev_t dev, u_long cmd, caddr_t data, int flags, struct ucred *cred
 	/* Really handled in upper layer */
 	case FIOASYNC:
 		break;
+	case FIONBIO:
+		break;
 	case MEM_SETIRQ:
 		intr = *(int16_t *)data;
 		if ((error = priv_check_cred(cred, PRIV_ROOT, 0)) != 0)
diff --git a/sys/kern/subr_log.c b/sys/kern/subr_log.c
index 6e174fa..1f60b11 100644
--- a/sys/kern/subr_log.c
+++ b/sys/kern/subr_log.c
@@ -281,6 +281,9 @@ logioctl(struct dev_ioctl_args *ap)
 		*(int *)ap->a_data = n;
 		break;
 
+	case FIONBIO:
+		break;
+
 	case FIOASYNC:
 		if (*(int *)ap->a_data)
 			atomic_set_int(&logsoftc.sc_state, LOG_ASYNC);
diff --git a/sys/kern/sys_pipe.c b/sys/kern/sys_pipe.c
index 951314f..5e0fa96 100644
--- a/sys/kern/sys_pipe.c
+++ b/sys/kern/sys_pipe.c
@@ -964,6 +964,9 @@ pipe_ioctl(struct file *fp, u_long cmd, caddr_t data,
 	lwkt_gettoken(&mpipe->pipe_wlock);
 
 	switch (cmd) {
+	case FIONBIO:
+		error = 0;
+		break;
 	case FIOASYNC:
 		if (*(int *)data) {
 			mpipe->pipe_state |= PIPE_ASYNC;
diff --git a/sys/kern/sys_socket.c b/sys/kern/sys_socket.c
index 8119523..cac7ffb 100644
--- a/sys/kern/sys_socket.c
+++ b/sys/kern/sys_socket.c
@@ -132,6 +132,9 @@ soo_ioctl(struct file *fp, u_long cmd, caddr_t data,
 	so = (struct socket *)fp->f_data;
 
 	switch (cmd) {
+	case FIONBIO:
+		error = 0;
+		break;
 	case FIOASYNC:
 		if (*(int *)data) {
 			sosetstate(so, SS_ASYNC);
diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index 27c4b1d..c527a5e 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -919,6 +919,8 @@ ttioctl(struct tty *tp, u_long cmd, void *data, int flag)
 			CLR(tp->t_state, TS_ASYNC);
 		crit_exit();
 		break;
+	case FIONBIO:
+		break;
 	case FIONREAD:			/* get # bytes to read */
 		crit_enter();
 		*(int *)data = ttnread(tp);
diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index 43f5296..2ad062f 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -916,7 +916,7 @@ vn_ioctl(struct file *fp, u_long com, caddr_t data, struct ucred *ucred,
 			error = 0;
 			break;
 		}
-		if (com == FIOASYNC) {				/* XXX */
+		if (com == FIOASYNC || com == FIONBIO) {	/* XXX */
 			error = 0;				/* XXX */
 			break;
 		}
diff --git a/sys/net/bpf.c b/sys/net/bpf.c
index 1a82aa1..38ddfed 100644
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -923,6 +923,9 @@ bpfioctl(struct dev_ioctl_args *ap)
 		d->bd_async = *(int *)ap->a_data;
 		break;
 
+	case FIONBIO:
+		break;
+
 	case FIOSETOWN:
 		error = fsetown(*(int *)ap->a_data, &d->bd_sigio);
 		break;
diff --git a/sys/net/tap/if_tap.c b/sys/net/tap/if_tap.c
index cd9b9b6..b14d7b5 100644
--- a/sys/net/tap/if_tap.c
+++ b/sys/net/tap/if_tap.c
@@ -752,6 +752,9 @@ tapioctl(struct dev_ioctl_args *ap)
 			tp->tap_flags &= ~TAP_ASYNC;
 		break;
 
+	case FIONBIO:
+		break;
+
 	case FIONREAD:
 		/* Take a look at devq first */
 		IF_POLL(&tp->tap_devq, mb);
diff --git a/sys/net/tun/if_tun.c b/sys/net/tun/if_tun.c
index 8f1b9ce..68752e8 100644
--- a/sys/net/tun/if_tun.c
+++ b/sys/net/tun/if_tun.c
@@ -491,6 +491,8 @@ tunioctl(struct dev_ioctl_args *ap)
 		else
 			tp->tun_flags &= ~TUN_ASYNC;
 		break;
+	case FIONBIO:
+		break;
 	case FIONREAD:
 		*(int *)ap->a_data = ifsq_poll_pktlen(
 		    ifq_get_subq_default(&tp->tun_if.if_snd));