diff --git a/libc/kernel/uapi/linux/xfrm.h b/libc/kernel/uapi/linux/xfrm.h
index e40b7e3..f4df95f 100644
--- a/libc/kernel/uapi/linux/xfrm.h
+++ b/libc/kernel/uapi/linux/xfrm.h
@@ -265,6 +265,7 @@
   XFRMA_SET_MARK,
   XFRMA_SET_MARK_MASK,
   XFRMA_IF_ID,
+  XFRMA_MTIMER_THRESH,
   __XFRMA_MAX
 #define XFRMA_OUTPUT_MARK XFRMA_SET_MARK
 #define XFRMA_MAX (__XFRMA_MAX - 1)