diff -urN mtools-3.9.6-orig/fat.c mtools-3.9.6/fat.c

--- mtools-3.9.6-orig/fat.c	Fri Apr 16 21:27:19 1999

+++ mtools-3.9.6/fat.c	Sat Aug  7 12:29:56 1999

@@ -608,6 +608,10 @@

 		 * and 0xff.  Do not consider this as an error */

 		return 0;

+

+	/* Some Atari ST disks are actually using f7/f9; ignore this

+	   "sanity check" to read them...

+	

 	if((address[0] != boot->descr && boot->descr >= 0xf0 &&

 	    (address[0] != 0xf9 || boot->descr != 0xf0)) ||

 	   address[0] < 0xf0) {

@@ -616,7 +620,7 @@

 				address[0],

 				boot->descr);

 		return -1;

-	}

+	} */

 	if(address[1] != 0xff || address[2] != 0xff){

 		fprintf(stderr,"Initial byte of fat is not 0xff\n");