diff --git a/net/netdev/netdev_ioctl.c b/net/netdev/netdev_ioctl.c
index 8cc035bce9..21d156afc5 100644
--- a/net/netdev/netdev_ioctl.c
+++ b/net/netdev/netdev_ioctl.c
@@ -1601,6 +1601,7 @@ ssize_t net_ioctl_arglen(int cmd)
 {
   switch (cmd)
     {
+      case FIONBIO:
       case FIONSPACE:
       case FIONREAD:
         return sizeof(int);