Index: uspace/srv/fs/exfat/exfat.h
===================================================================
--- uspace/srv/fs/exfat/exfat.h	(revision 998a78f1b5dbd9331dfc51ef01dde3562a3a6cc4)
+++ uspace/srv/fs/exfat/exfat.h	(revision 7be14db249abeccfaa0b527e6c0e0e8fd4220977)
@@ -50,6 +50,7 @@
 #define BS_SIZE			512
 
-#define BPS(bs)			(1 << (bs->bytes_per_sector))
-#define SPC(bs)			(1 << (bs->sec_per_cluster))
+#define BPS(bs)			((uint32_t) (1 << (bs->bytes_per_sector)))
+#define SPC(bs)			((uint32_t)(1 << (bs->sec_per_cluster)))
+#define BPC(bs)			((uint32_t)(BPS(bs)*SPC(bs)))
 #define VOL_FS(bs)		uint64_t_le2host(bs->volume_start)
 #define VOL_CNT(bs)		uint64_t_le2host(bs->volume_count)