Index: uspace/app/mkexfat/mkexfat.c
===================================================================
--- uspace/app/mkexfat/mkexfat.c	(revision 3938375d8bed4c6ef08c2745c97f2e144f33dbf5)
+++ uspace/app/mkexfat/mkexfat.c	(revision b0fecad6d896010a48a55ba72f369a908bf1996e)
@@ -319,13 +319,20 @@
 	pfat[1] = host2uint32_t_le(0xFFFFFFFF);
 
+	/* Allocate clusters for the bitmap, upcase table
+	 * and the root directory.
+	 */
+	pfat[2] = host2uint32_t_le(0xFFFFFFFF);
+	pfat[3] = host2uint32_t_le(0xFFFFFFFF);
+	pfat[4] = host2uint32_t_le(0xFFFFFFFF);
+
 	rc = block_write_direct(service_id, FAT_SECTOR_START, 1, pfat);
 	if (rc != EOK)
 		goto error;
 
-	pfat[0] = pfat[1] = 0x00000000;
-
-	for (i = 1; i < cfg->fat_sector_count; ++i) {
+	memset(pfat, 0, 5 * sizeof(uint32_t));
+
+	for (i = 1; i < cfg->fat_sector_count + 1; ++i) {
 		rc = block_write_direct(service_id,
-		    FAT_SECTOR_START + i + 1, 1, pfat);
+		    FAT_SECTOR_START + i, 1, pfat);
 		if (rc != EOK)
 			goto error;