diff --git a/csum-file.h b/csum-file.h
index f9cbd317fb..e54d53d1d0 100644
--- a/csum-file.h
+++ b/csum-file.h
@@ -62,4 +62,11 @@ static inline void hashwrite_be32(struct hashfile *f, uint32_t data)
 	hashwrite(f, &data, sizeof(data));
 }
 
+static inline size_t hashwrite_be64(struct hashfile *f, uint64_t data)
+{
+	data = htonll(data);
+	hashwrite(f, &data, sizeof(data));
+	return sizeof(data);
+}
+
 #endif