diff --git a/tools/lib/traceevent/event-parse.h b/tools/lib/traceevent/event-parse.h
index 6abda54..84e554f 100644
--- a/tools/lib/traceevent/event-parse.h
+++ b/tools/lib/traceevent/event-parse.h
@@ -599,7 +599,7 @@
 };
 
 int pevent_register_comm(struct pevent *pevent, const char *comm, int pid);
-void pevent_register_trace_clock(struct pevent *pevent, char *trace_clock);
+int pevent_register_trace_clock(struct pevent *pevent, const char *trace_clock);
 int pevent_register_function(struct pevent *pevent, char *name,
 			     unsigned long long addr, char *mod);
 int pevent_register_print_string(struct pevent *pevent, const char *fmt,