diff --git a/VoldUtil.h b/VoldUtil.h
index 30a3add..469489a 100644
--- a/VoldUtil.h
+++ b/VoldUtil.h
@@ -17,6 +17,12 @@
 #ifndef _VOLDUTIL_H
 #define _VOLDUTIL_H
 
+#include <sys/cdefs.h>
+
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof(*(a)))
 
+__BEGIN_DECLS
+  unsigned int get_blkdev_size(int fd);
+__END_DECLS
+
 #endif