diff --git a/fio.h b/fio.h
index 49ddd92..d36ee16 100644
--- a/fio.h
+++ b/fio.h
@@ -650,6 +650,7 @@
 extern enum fio_cs fio_clock_source;
 extern int warnings_fatal;
 extern int terse_version;
+extern int is_backend;
 
 extern struct thread_data *threads;