diff --git a/sbin/fsck_ext2fs/setup.c b/sbin/fsck_ext2fs/setup.c
index 0c7c0164680..686cbb45fb4 100644
--- a/sbin/fsck_ext2fs/setup.c
+++ b/sbin/fsck_ext2fs/setup.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: setup.c,v 1.35 2024/12/18 10:36:05 sthen Exp $	*/
+/*	$OpenBSD: setup.c,v 1.36 2025/09/17 16:07:57 deraadt Exp $	*/
 /*	$NetBSD: setup.c,v 1.1 1997/06/11 11:22:01 bouyer Exp $	*/
 
 /*
@@ -455,7 +455,7 @@ calcsb(char *dev, int devfd, struct m_ext2fs *fs, struct disklabel *lp)
 	char *cp;
 
 	cp = strchr(dev, '\0');
-	if ((cp == NULL || (cp[-1] < 'a' || cp[-1] >= 'a' + MAXPARTITIONS)) &&
+	if ((cp == NULL || DL_PARTNAME2NUM(cp[-1]) == -1) &&
 	    !isdigit((unsigned char)cp[-1])) {
 		pfatal("%s: CANNOT FIGURE OUT FILE SYSTEM PARTITION\n", dev);
 		return (0);
@@ -466,7 +466,7 @@ calcsb(char *dev, int devfd, struct m_ext2fs *fs, struct disklabel *lp)
 	if (isdigit((unsigned char)*cp))
 		pp = &lp->d_partitions[0];
 	else
-		pp = &lp->d_partitions[*cp - 'a'];
+		pp = &lp->d_partitions[DL_PARTNAME2NUM(*cp)];
 	if (pp->p_fstype != FS_EXT2FS) {
 		pfatal("%s: NOT LABELED AS A EXT2 FILE SYSTEM (%s)\n",
 			dev, pp->p_fstype < FSMAXTYPES ?
diff --git a/sbin/fsck_ffs/setup.c b/sbin/fsck_ffs/setup.c
index 72e77f40a78..2f3a500bd75 100644
--- a/sbin/fsck_ffs/setup.c
+++ b/sbin/fsck_ffs/setup.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: setup.c,v 1.71 2025/02/26 06:18:56 otto Exp $	*/
+/*	$OpenBSD: setup.c,v 1.72 2025/09/17 16:07:57 deraadt Exp $	*/
 /*	$NetBSD: setup.c,v 1.27 1996/09/27 22:45:19 christos Exp $	*/
 
 /*
@@ -614,7 +614,7 @@ calcsb(char *dev, int devfd, struct fs *fs, struct disklabel *lp,
 	int i;
 
 	cp = strchr(dev, '\0');
-	if ((cp == NULL || (cp[-1] < 'a' || cp[-1] >= 'a' + MAXPARTITIONS)) &&
+	if ((cp == NULL || DL_PARTNAME2NUM(cp[-1]) == -1) &&
 	    !isdigit((unsigned char)cp[-1])) {
 		pfatal("%s: CANNOT FIGURE OUT FILE SYSTEM PARTITION\n", dev);
 		return (0);
@@ -627,7 +627,7 @@ calcsb(char *dev, int devfd, struct fs *fs, struct disklabel *lp,
 	if (isdigit((unsigned char)*cp))
 		pp = &lp->d_partitions[0];
 	else
-		pp = &lp->d_partitions[*cp - 'a'];
+		pp = &lp->d_partitions[DL_PARTNAME2NUM(*cp)];
 	if (pp->p_fstype != FS_BSDFFS) {
 		pfatal("%s: NOT LABELED AS A BSD FILE SYSTEM (%s)\n",
 		    dev, pp->p_fstype < FSMAXTYPES ?
diff --git a/sbin/newfs/newfs.c b/sbin/newfs/newfs.c
index 94c023a3aad..be78f2b40df 100644
--- a/sbin/newfs/newfs.c
+++ b/sbin/newfs/newfs.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: newfs.c,v 1.119 2025/09/17 10:51:17 deraadt Exp $	*/
+/*	$OpenBSD: newfs.c,v 1.120 2025/09/17 16:07:57 deraadt Exp $	*/
 /*	$NetBSD: newfs.c,v 1.20 1996/05/16 07:13:03 thorpej Exp $	*/
 
 /*
@@ -424,8 +424,7 @@ main(int argc, char *argv[])
 		if (*argv[0] == '\0')
 			fatal("empty partition name supplied");
 		cp = argv[0] + strlen(argv[0]) - 1;
-		if ((*cp < 'a' || *cp > ('a' + maxpartitions - 1))
-		    && !isdigit((unsigned char)*cp))
+		if (DL_PARTNAME2NUM(*cp) == -1 && !isdigit((unsigned char)*cp))
 			fatal("%s: can't figure out file system partition",
 			    argv[0]);
 		lp = getdisklabel(special, fsi);
@@ -436,7 +435,7 @@ main(int argc, char *argv[])
 		if (isdigit((unsigned char)*cp))
 			pp = &lp->d_partitions[0];
 		else
-			pp = &lp->d_partitions[*cp - 'a'];
+			pp = &lp->d_partitions[DL_PARTNAME2NUM(*cp)];
 		if (DL_GETPSIZE(pp) == 0)
 			fatal("%s: `%c' partition is unavailable",
 			    argv[0], *cp);
diff --git a/sbin/newfs_ext2fs/newfs_ext2fs.c b/sbin/newfs_ext2fs/newfs_ext2fs.c
index f7e48286f7c..62b3d6beee9 100644
--- a/sbin/newfs_ext2fs/newfs_ext2fs.c
+++ b/sbin/newfs_ext2fs/newfs_ext2fs.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: newfs_ext2fs.c,v 1.29 2022/12/04 23:50:47 cheloha Exp $ */
+/* $OpenBSD: newfs_ext2fs.c,v 1.30 2025/09/17 16:07:57 deraadt Exp $ */
 /*	$NetBSD: newfs_ext2fs.c,v 1.8 2009/03/02 10:38:13 tsutsui Exp $	*/
 
 /*
@@ -478,14 +478,13 @@ getpartition(int fsi, const char *special, char *argv[], struct disklabel **dl)
 	if (*argv[0] == '\0')
 		errx(EXIT_FAILURE, "empty partition name supplied");
 	cp = argv[0] + strlen(argv[0]) - 1;
-	if ((*cp < 'a' || *cp > ('a' + getmaxpartitions() - 1))
-	    && !isdigit((unsigned char)*cp))
+	if (DL_PARTNAME2NUM(*cp) == -1 && !isdigit((unsigned char)*cp))
 		errx(EXIT_FAILURE, "%s: can't figure out file system partition", argv[0]);
 	lp = getdisklabel(special, fsi);
 	if (isdigit((unsigned char)*cp))
 		pp = &lp->d_partitions[0];
 	else
-		pp = &lp->d_partitions[*cp - 'a'];
+		pp = &lp->d_partitions[DL_PARTNAME2NUM(*cp)];
 	if (DL_GETPSIZE(pp) == 0) 
 		errx(EXIT_FAILURE, "%s: `%c' partition is unavailable", argv[0], *cp);
 	*dl = lp;
diff --git a/sbin/newfs_msdos/newfs_msdos.c b/sbin/newfs_msdos/newfs_msdos.c
index 0cc837778d8..df3bc1a332b 100644
--- a/sbin/newfs_msdos/newfs_msdos.c
+++ b/sbin/newfs_msdos/newfs_msdos.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: newfs_msdos.c,v 1.29 2024/04/28 16:43:42 florian Exp $	*/
+/*	$OpenBSD: newfs_msdos.c,v 1.30 2025/09/17 16:07:57 deraadt Exp $	*/
 
 /*
  * Copyright (c) 1998 Robert Nordier
@@ -727,9 +727,8 @@ getdiskinfo(int fd, const char *fname, const char *dtype, int oflag,
     else
 	while (isdigit((unsigned char)*++s2));
     s1 = s2;
-    if (s2 && *s2 >= 'a' && *s2 <= 'a' + MAXPARTITIONS - 1) {
-	part = *s2++ - 'a';
-    }
+    if (s2)
+	part = DL_PARTNAME2NUM(*s2++);
     if (!s2 || (*s2 && *s2 != '.'))
 	errx(1, "%s: can't figure out partition info", fname);
     if ((((!oflag && part != -1) || !bpb->bsec)) ||