diff --git a/libc/kernel/uapi/linux/tcp.h b/libc/kernel/uapi/linux/tcp.h
index ce3d735..1ec025f 100644
--- a/libc/kernel/uapi/linux/tcp.h
+++ b/libc/kernel/uapi/linux/tcp.h
@@ -92,6 +92,7 @@
 #define TCP_ZEROCOPY_RECEIVE 35
 #define TCP_INQ 36
 #define TCP_CM_INQ TCP_INQ
+#define TCP_TX_DELAY 37
 #define TCP_REPAIR_ON 1
 #define TCP_REPAIR_OFF 0
 #define TCP_REPAIR_OFF_NO_WP - 1