diff --git a/usr.sbin/bhyve/slirp/slirp-helper.c b/usr.sbin/bhyve/slirp/slirp-helper.c
--- a/usr.sbin/bhyve/slirp/slirp-helper.c
+++ b/usr.sbin/bhyve/slirp/slirp-helper.c
@@ -503,6 +503,8 @@
 
 	memset(&priv, 0, sizeof(priv));
 	priv.sock = sd;
+	if (ioctl(priv.sock, FIONBIO, &(int){0}) == -1)
+		err(1, "ioctl(FIONBIO)");
 	if (pipe2(priv.wakeup, O_CLOEXEC | O_NONBLOCK) != 0)
 		err(1, "pipe2");