diff --git a/os/os.h b/os/os.h
index cbb476f..c10cb12 100644
--- a/os/os.h
+++ b/os/os.h
@@ -129,6 +129,10 @@
 #define FIO_OS_PATH_SEPARATOR	"/"
 #endif
 
+#ifndef FIO_PREFERRED_CLOCK_SOURCE
+#define FIO_PREFERRED_CLOCK_SOURCE	CS_CGETTIME
+#endif
+
 #ifndef FIO_MAX_JOBS
 #define FIO_MAX_JOBS		2048
 #endif