diff --git a/fio.h b/fio.h
index 3de3f00..de4ca4d 100644
--- a/fio.h
+++ b/fio.h
@@ -598,6 +598,7 @@
 extern int fio_gtod_offload;
 extern int fio_gtod_cpu;
 extern enum fio_cs fio_clock_source;
+extern int fio_clock_source_set;
 extern int warnings_fatal;
 extern int terse_version;
 extern int is_backend;