Index: sys/kern/subr_disk_mbr.c
===================================================================
RCS file: /cvsroot/src/sys/kern/subr_disk_mbr.c,v
retrieving revision 1.51
diff -u -r1.51 subr_disk_mbr.c
--- sys/kern/subr_disk_mbr.c	17 May 2019 18:50:40 -0000	1.51
+++ sys/kern/subr_disk_mbr.c	6 Nov 2019 12:24:02 -0000
@@ -571,8 +571,11 @@
 static bool
 check_label_magic(const struct disklabel *dlp, uint32_t diskmagic)
 {
-	return memcmp(&dlp->d_magic, &diskmagic, sizeof(diskmagic)) == 0 &&
-	    memcmp(&dlp->d_magic2, &diskmagic, sizeof(diskmagic)) == 0;
+
+	return memcmp((const char *)dlp + offsetof(struct disklabel, d_magic),
+	              &diskmagic, sizeof(diskmagic)) == 0 &&
+	    memcmp((const char *)dlp + offsetof(struct disklabel, d_magic2),
+	           &diskmagic, sizeof(diskmagic)) == 0;
 }
 
 #ifdef DISKLABEL_EI