diff --git a/include/sys/vdev.h b/include/sys/vdev.h
index c2ad8c36dfcf..38f62b07dc59 100644
--- a/include/sys/vdev.h
+++ b/include/sys/vdev.h
@@ -209,6 +209,7 @@ extern void vdev_label_write(zio_t *zio, vdev_t *vd, int l, abd_t *buf, uint64_t
 extern int vdev_label_read_bootenv(vdev_t *, nvlist_t *);
 extern int vdev_label_write_bootenv(vdev_t *, nvlist_t *);
 extern int vdev_uberblock_sync_list(vdev_t **, int, struct uberblock *, int);
+extern int vdev_check_boot_reserve(spa_t *, vdev_t *);
 
 typedef enum {
 	VDEV_LABEL_CREATE,	/* create/add a new device */
diff --git a/lib/libzfs/libzfs_pool.c b/lib/libzfs/libzfs_pool.c
index 8a4e9939137a..7c63d072476f 100644
--- a/lib/libzfs/libzfs_pool.c
+++ b/lib/libzfs/libzfs_pool.c
@@ -3520,8 +3520,8 @@ zpool_vdev_attach(zpool_handle_t *zhp, const char *old_disk,
 		break;
 
 	case EBUSY:
-		zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
-		"%s is busy"), new_disk);
+		zfs_error_aux(hdl, dgettext(TEXT_DOMAIN, "%s is busy"),
+		    new_disk);
 		(void) zfs_error(hdl, EZFS_BADDEV, errbuf);
 		break;
 
@@ -3561,9 +3561,23 @@ zpool_vdev_attach(zpool_handle_t *zhp, const char *old_disk,
 			    "being replaced"));
 			(void) zfs_error(hdl, EZFS_BADDEV, errbuf);
 			break;
+		} else {
+			(void) zpool_standard_error(hdl, errno, errbuf);
 		}
-		/* fall through */
+		break;
 
+	case EADDRINUSE:
+		/*
+		 * The boot reserved area is already being used (FreeBSD)
+		 */
+		if (strcmp(type, VDEV_TYPE_RAIDZ) == 0) {
+			zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+			    "the reserved boot area needed for the expansion "
+			    "is already being used by a boot loader"));
+		} else {
+			(void) zpool_standard_error(hdl, errno, errbuf);
+		}
+		break;
 	default:
 		(void) zpool_standard_error(hdl, errno, errbuf);
 	}
diff --git a/lib/libzpool/Makefile.am b/lib/libzpool/Makefile.am
index 58d7f07527aa..3c986a707d2d 100644
--- a/lib/libzpool/Makefile.am
+++ b/lib/libzpool/Makefile.am
@@ -43,6 +43,7 @@ nodist_libzpool_la_SOURCES = \
 	module/os/linux/zfs/arc_os.c \
 	module/os/linux/zfs/trace.c \
 	module/os/linux/zfs/vdev_file.c \
+	module/os/linux/zfs/vdev_label_os.c \
 	module/os/linux/zfs/zfs_debug.c \
 	module/os/linux/zfs/zfs_racct.c \
 	module/os/linux/zfs/zfs_znode.c \
diff --git a/module/Kbuild.in b/module/Kbuild.in
index 485331ac655e..a0cd584d19dc 100644
--- a/module/Kbuild.in
+++ b/module/Kbuild.in
@@ -445,6 +445,7 @@ ZFS_OBJS_OS := \
 	trace.o \
 	vdev_disk.o \
 	vdev_file.o \
+	vdev_label_os.o \
 	zfs_acl.o \
 	zfs_ctldir.o \
 	zfs_debug.o \
diff --git a/module/os/freebsd/zfs/vdev_label_os.c b/module/os/freebsd/zfs/vdev_label_os.c
index bc856b930235..338982ff6873 100644
--- a/module/os/freebsd/zfs/vdev_label_os.c
+++ b/module/os/freebsd/zfs/vdev_label_os.c
@@ -72,3 +72,62 @@ vdev_label_write_pad2(vdev_t *vd, const char *buf, size_t size)
 	abd_free(pad2);
 	return (error);
 }
+
+static void
+vdev_child_done(zio_t *zio)
+{
+	zio_t *pio = zio->io_private;
+
+	mutex_enter(&pio->io_lock);
+	pio->io_error = zio_worst_error(pio->io_error, zio->io_error);
+	mutex_exit(&pio->io_lock);
+}
+
+/*
+ * Check if the reserved boot area is in-use.
+ *
+ * When booting FreeBSD with an MBR partition with ZFS, the zfsboot file
+ * (which understands the ZFS file system) is written to the ZFS BOOT
+ * reserve area (at offset 512K). We check for that here before attaching
+ * a disk to raidz which would then corrupt this boot data.
+ */
+int
+vdev_check_boot_reserve(spa_t *spa, vdev_t *childvd)
+{
+	ASSERT(childvd->vdev_ops->vdev_op_leaf);
+
+	size_t size = SPA_MINBLOCKSIZE;
+	abd_t *abd = abd_alloc_linear(size, B_FALSE);
+
+	zio_t *pio = zio_root(spa, NULL, NULL, 0);
+	/*
+	 * Note: zio_vdev_child_io() adds VDEV_LABEL_START_SIZE to the offset
+	 * to calculate the physical offset to write to.  Passing in a negative
+	 * offset lets us access the boot area.
+	 */
+	zio_nowait(zio_vdev_child_io(pio, NULL, childvd,
+	    VDEV_BOOT_OFFSET - VDEV_LABEL_START_SIZE, abd, size, ZIO_TYPE_READ,
+	    ZIO_PRIORITY_ASYNC_READ, 0, vdev_child_done, pio));
+	zio_wait(pio);
+
+	unsigned char *buf = abd_to_buf(abd);
+
+	/*
+	 * The BTX server has a special header at the begining.
+	 *
+	 * btx_hdr:	.byte 0xeb		# Machine ID
+	 *		.byte 0xe		# Header size
+	 *		.ascii "BTX"		# Magic
+	 *		.byte 0x1		# Major version
+	 *		.byte 0x2		# Minor version
+	 *		.byte BTX_FLAGS		# Flags
+	 */
+	if (buf[0] == 0xeb && buf[1] == 0x0e &&
+	    buf[2] == 'B' && buf[3] == 'T' && buf[4] == 'X') {
+		abd_free(abd);
+		return (EBUSY);
+	}
+
+	abd_free(abd);
+	return (0);
+}
diff --git a/module/os/linux/zfs/vdev_label_os.c b/module/os/linux/zfs/vdev_label_os.c
new file mode 100644
index 000000000000..f0325d84b797
--- /dev/null
+++ b/module/os/linux/zfs/vdev_label_os.c
@@ -0,0 +1,44 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or https://opensource.org/licenses/CDDL-1.0.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2023 by iXsystems, Inc.
+ */
+
+#include <sys/zfs_context.h>
+#include <sys/spa.h>
+#include <sys/spa_impl.h>
+#include <sys/vdev.h>
+#include <sys/vdev_impl.h>
+
+/*
+ * Check if the reserved boot area is in-use.
+ *
+ * Not aware of any external uses on Linux.
+ */
+int
+vdev_check_boot_reserve(spa_t *spa, vdev_t *childvd)
+{
+	(void) spa;
+	(void) childvd;
+
+	return (0);
+}
diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index a8f5e9e2d55f..28c93714475e 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -7059,6 +7059,12 @@ spa_vdev_attach(spa_t *spa, uint64_t guid, nvlist_t *nvroot, int replacing,
 				return (spa_vdev_exit(spa, newrootvd, txg,
 				    ENXIO));
 			}
+			/* Also fail if reserved boot area is in-use */
+			if (vdev_check_boot_reserve(spa, oldvd->vdev_child[i])
+			    != 0) {
+				return (spa_vdev_exit(spa, newrootvd, txg,
+				    EADDRINUSE));
+			}
 		}
 	}
 
diff --git a/module/zfs/vdev_raidz.c b/module/zfs/vdev_raidz.c
index c2df04bfbf69..46239cc8cefe 100644
--- a/module/zfs/vdev_raidz.c
+++ b/module/zfs/vdev_raidz.c
@@ -207,7 +207,7 @@
  * context. The design also allows for fast discovery of what data to copy.
  *
  * The VDEV metaslabs are processed, one at a time, to copy the block data to
- * have it flow across all the disks. The metasab is disabled for allocations
+ * have it flow across all the disks. The metaslab is disabled for allocations
  * during the copy. As an optimization, we only copy the allocated data which
  * can be determined by looking at the metaslab range tree. During the copy we
  * must maintain the redundancy guarantees of the RAIDZ VDEV (e.g. parity count
@@ -267,7 +267,7 @@
  *
  * == Reflow Progress Updates ==
  * After the initial scratch-based reflow, the expansion process works
- * similarly to device removal. We create a new open context thread whichi
+ * similarly to device removal. We create a new open context thread which
  * reflows the data, and periodically kicks off sync tasks to update logical
  * state. In this case, state is the committed progress (offset of next data
  * to copy). We need to persist the completed offset on disk, so that if we
diff --git a/tests/runfiles/common.run b/tests/runfiles/common.run
index e0fea3d68d32..57e82db7f1ee 100644
--- a/tests/runfiles/common.run
+++ b/tests/runfiles/common.run
@@ -772,7 +772,7 @@ tags = ['functional', 'redacted_send']
 tests = ['raidz_001_neg', 'raidz_002_pos', 'raidz_003_pos', 'raidz_004_pos',
     'raidz_expand_001_pos', 'raidz_expand_002_pos', 'raidz_expand_003_neg',
     'raidz_expand_003_pos', 'raidz_expand_004_pos', 'raidz_expand_005_pos',
-    'raidz_expand_006_neg']
+    'raidz_expand_006_neg', 'raidz_expand_007_neg']
 tags = ['functional', 'raidz']
 timeout = 1200
 
diff --git a/tests/zfs-tests/tests/Makefile.am b/tests/zfs-tests/tests/Makefile.am
index 6f4565fdabf5..8acedf935985 100644
--- a/tests/zfs-tests/tests/Makefile.am
+++ b/tests/zfs-tests/tests/Makefile.am
@@ -1655,6 +1655,7 @@ nobase_dist_datadir_zfs_tests_tests_SCRIPTS += \
 	functional/raidz/raidz_expand_004_pos.ksh \
 	functional/raidz/raidz_expand_005_pos.ksh \
 	functional/raidz/raidz_expand_006_neg.ksh \
+	functional/raidz/raidz_expand_007_neg.ksh \
 	functional/raidz/setup.ksh \
 	functional/redacted_send/cleanup.ksh \
 	functional/redacted_send/redacted_compressed.ksh \
diff --git a/tests/zfs-tests/tests/functional/raidz/raidz_expand_007_neg.ksh b/tests/zfs-tests/tests/functional/raidz/raidz_expand_007_neg.ksh
new file mode 100755
index 000000000000..78294cb9e516
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/raidz/raidz_expand_007_neg.ksh
@@ -0,0 +1,86 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or http://www.opensolaris.org/os/licensing.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2023 by iXsystems, Inc.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# DESCRIPTION:
+# 	Negative for FreeBSD Only
+#
+#	Attempting to expand a RAIDZ should fail if the scratch area on the
+#	existing disks contains BTX Server binary (used to boot FreeBSD when
+#	using MBR partitions with ZFS).
+#
+# STRATEGY:
+#	1. Create raidz pool
+#	2. Add a BTX header to the reserved boot area
+#	3. Attempt to attach a device to the raidz vdev
+#	4. Verify that device attached failed
+#	5. Destroy the raidz pool
+
+typeset -r devs=4
+typeset -r dev_size_mb=128
+typeset -a disks
+
+function cleanup
+{
+	log_pos zpool status "$TESTPOOL"
+
+	poolexists "$TESTPOOL" && log_must_busy zpool destroy "$TESTPOOL"
+
+	for i in {0..$devs}; do
+		log_must rm -f "$TEST_BASE_DIR/dev-$i"
+	done
+}
+
+log_onexit cleanup
+
+for i in {0..$devs}; do
+	device=$TEST_BASE_DIR/dev-$i
+	# simulate active BTX Server data by inserting a BTX header
+	printf "\xeb\x0e%s\x01\x02\x80" "BTX" | dd of="$device" \
+		bs=512 seek=1024 status=none
+	log_must truncate -s ${dev_size_mb}M "$device"
+	if [[ $i -ne $devs ]]; then
+		disks[${#disks[*]}+1]=$device
+	fi
+done
+
+log_must zpool create -f -o cachefile=none "$TESTPOOL" raidz1 "${disks[@]}"
+
+if is_freebsd; then
+	# expecting attach to fail
+	log_mustnot_expect "the reserved boot area" zpool attach -f \
+		"$TESTPOOL" raidz1-0 "$TEST_BASE_DIR/dev-$devs"
+	log_must zpool destroy "$TESTPOOL"
+	log_pass "raidz attach failed with in-use reserved boot area"
+else
+	# expecting attach to pass everywhere else
+	log_must zpool attach -f "$TESTPOOL" raidz1-0 "$TEST_BASE_DIR/dev-$devs"
+	log_must zpool destroy "$TESTPOOL"
+	log_pass "raidz attach passed with in-use reserved boot area"
+fi
+