diff --git a/Userland/Libraries/LibC/sys/ioctl_numbers.h b/Userland/Libraries/LibC/sys/ioctl_numbers.h
index fbd3fefe57..0d70d7f63a 100644
--- a/Userland/Libraries/LibC/sys/ioctl_numbers.h
+++ b/Userland/Libraries/LibC/sys/ioctl_numbers.h
@@ -93,6 +93,7 @@ enum IOCtlNumber {
     KEYBOARD_IOCTL_SET_NUM_LOCK,
     KEYBOARD_IOCTL_GET_CAPS_LOCK,
     KEYBOARD_IOCTL_SET_CAPS_LOCK,
+    SIOCATMARK,
     SIOCSIFADDR,
     SIOCGIFADDR,
     SIOCGIFHWADDR,
@@ -141,6 +142,7 @@ enum IOCtlNumber {
 #define KEYBOARD_IOCTL_SET_NUM_LOCK KEYBOARD_IOCTL_SET_NUM_LOCK
 #define KEYBOARD_IOCTL_GET_CAPS_LOCK KEYBOARD_IOCTL_GET_CAPS_LOCK
 #define KEYBOARD_IOCTL_SET_CAPS_LOCK KEYBOARD_IOCTL_SET_CAPS_LOCK
+#define SIOCATMARK SIOCATMARK
 #define SIOCSIFADDR SIOCSIFADDR
 #define SIOCGIFADDR SIOCGIFADDR
 #define SIOCGIFHWADDR SIOCGIFHWADDR