diff --git a/libc/kernel/uapi/linux/fcntl.h b/libc/kernel/uapi/linux/fcntl.h
index e98a67b..66f27b6 100644
--- a/libc/kernel/uapi/linux/fcntl.h
+++ b/libc/kernel/uapi/linux/fcntl.h
@@ -32,6 +32,7 @@
 #define F_SEAL_SHRINK 0x0002
 #define F_SEAL_GROW 0x0004
 #define F_SEAL_WRITE 0x0008
+#define F_SEAL_FUTURE_WRITE 0x0010
 #define F_GET_RW_HINT (F_LINUX_SPECIFIC_BASE + 11)
 #define F_SET_RW_HINT (F_LINUX_SPECIFIC_BASE + 12)
 #define F_GET_FILE_RW_HINT (F_LINUX_SPECIFIC_BASE + 13)