Index: fs/fat.c
===================================================================
--- fs/fat.c	(revision 1987)
+++ fs/fat.c	(working copy)
@@ -187,9 +187,9 @@
   if (grub_disk_read (disk, 0, 0, sizeof (bpb), (char *) &bpb))
     goto fail;
 
-  if (! grub_strncmp((const char *) bpb.version_specific.fat12_or_fat16.fstype, "FAT12",5)
-      || ! grub_strncmp((const char *) bpb.version_specific.fat12_or_fat16.fstype, "FAT16",5)
-      || ! grub_strncmp((const char *) bpb.version_specific.fat32.fstype, "FAT32",5))
+  if (0 != grub_strncmp((const char *) bpb.version_specific.fat12_or_fat16.fstype, "FAT12", 5)
+      && 0 != grub_strncmp((const char *) bpb.version_specific.fat12_or_fat16.fstype, "FAT16", 5)
+      && 0 != grub_strncmp((const char *) bpb.version_specific.fat32.fstype, "FAT32", 5))
     goto fail;
   
   /* Get the sizes of logical sectors and clusters.  */