diff --git a/libc/kernel/uapi/linux/counter.h b/libc/kernel/uapi/linux/counter.h
index 091e33d..4b86b28 100644
--- a/libc/kernel/uapi/linux/counter.h
+++ b/libc/kernel/uapi/linux/counter.h
@@ -45,6 +45,7 @@
   COUNTER_EVENT_OVERFLOW_UNDERFLOW,
   COUNTER_EVENT_THRESHOLD,
   COUNTER_EVENT_INDEX,
+  COUNTER_EVENT_CHANGE_OF_STATE,
 };
 struct counter_watch {
   struct counter_component component;