diff --git a/exfat/mkfs/mkexfat.h b/exfat/mkfs/mkexfat.h
index 8d2b5e3..6e15c59 100644
--- a/exfat/mkfs/mkexfat.h
+++ b/exfat/mkfs/mkexfat.h
@@ -27,8 +27,8 @@
 
 struct fs_object
 {
-	off_t (*get_alignment)(void);
-	off_t (*get_size)(void);
+	loff_t (*get_alignment)(void);
+	loff_t (*get_size)(void);
 	int (*write)(struct exfat_dev* dev);
 };
 
@@ -36,14 +36,14 @@
 
 int get_sector_bits(void);
 int get_spc_bits(void);
-off_t get_volume_size(void);
+loff_t get_volume_size(void);
 const le16_t* get_volume_label(void);
 uint32_t get_volume_serial(void);
 uint64_t get_first_sector(void);
 int get_sector_size(void);
 int get_cluster_size(void);
 
-int mkfs(struct exfat_dev* dev, off_t volume_size);
-off_t get_position(const struct fs_object* object);
+int mkfs(struct exfat_dev* dev, loff_t volume_size);
+loff_t get_position(const struct fs_object* object);
 
 #endif /* ifndef MKFS_MKEXFAT_H_INCLUDED */