Index: uspace/app/mkfat/mkfat.c
===================================================================
--- uspace/app/mkfat/mkfat.c	(revision ede7ae19c371b877015a5238d24e3f5e817318d0)
+++ uspace/app/mkfat/mkfat.c	(revision 462b418bff979160ff8af9f9916ba81d26cc59cd)
@@ -189,4 +189,9 @@
 	}
 
+	if (cfg.fat_type != FAT12 && cfg.fat_type != FAT16 && cfg.fat_type != FAT32) {
+		printf(NAME ": Error. Unknown FAT type.\n");
+		return 2;
+	}
+
 	printf(NAME ": Creating FAT%d filesystem on device %s.\n", cfg.fat_type, dev_path);