diff --git a/lib/rbcodec/test/file.h b/lib/rbcodec/test/file.h
index b673fa8f93..ddf9a1d7a4 100644
--- a/lib/rbcodec/test/file.h
+++ b/lib/rbcodec/test/file.h
@@ -2,3 +2,5 @@
 #define MAX_PATH 260
 #include <unistd.h>
 #include <fcntl.h>
+
+off_t filesize(int fd);