diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 441992a..f34dab9 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -671,6 +671,7 @@
 	enum perf_event_active_state	state;
 	unsigned int			attach_state;
 	atomic64_t			count;
+	atomic64_t			child_count;
 
 	/*
 	 * These are the total time in nanoseconds that the event