Apply by doing:
        cd /usr/src
        patch -p0 < 001_st.patch

Rebuild your kernel.

Index: sys/scsi/st.c
===================================================================
RCS file: /cvs/src/sys/scsi/st.c,v
retrieving revision 1.41
retrieving revision 1.41.2.1
diff -u -p -r1.41 -r1.41.2.1
--- sys/scsi/st.c	1 Aug 2004 23:01:06 -0000	1.41
+++ sys/scsi/st.c	2 Nov 2004 01:05:50 -0000	1.41.2.1
@@ -1815,7 +1815,7 @@ st_interpret_sense(xs)
 	u_int8_t skey = sense->flags & SSD_KEY;
 	int32_t info;
 
-	if (((sense->flags & SDEV_OPEN) == 0) ||
+	if (((sc_link->flags & SDEV_OPEN) == 0) ||
 	    (serr != 0x70 && serr != 0x71))
 		return (EJUSTRETURN); /* let the generic code handle it */