diff --git a/userspace/libraries/LibC/include/sys/ioctl.h b/userspace/libraries/LibC/include/sys/ioctl.h
index fe7627c7..bf50157e 100644
--- a/userspace/libraries/LibC/include/sys/ioctl.h
+++ b/userspace/libraries/LibC/include/sys/ioctl.h
@@ -38,6 +38,7 @@ __BEGIN_DECLS
 #define KDLOADFONT	30
 
 #define FIONREAD	40 /* get number of input bytes available */
+#define FIONBIO		41
 
 struct winsize
 {