diff --git a/tools/perf/util/cgroup.h b/tools/perf/util/cgroup.h
index de5b272..12256b7 100644
--- a/tools/perf/util/cgroup.h
+++ b/tools/perf/util/cgroup.h
@@ -18,6 +18,7 @@ struct cgroup {
 };
 
 extern int nr_cgroups; /* number of explicit cgroups defined */
+extern bool cgrp_event_expanded;
 
 struct cgroup *cgroup__get(struct cgroup *cgroup);
 void cgroup__put(struct cgroup *cgroup);