diff --git a/usr.sbin/makefs/zfs.c b/usr.sbin/makefs/zfs.c
index 08689a55887..ab6011046b2 100644
--- a/usr.sbin/makefs/zfs.c
+++ b/usr.sbin/makefs/zfs.c
@@ -34,6 +34,7 @@
 
 #include <assert.h>
 #include <fcntl.h>
+#include <stdalign.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdlib.h>
@@ -69,7 +70,13 @@ struct dnode_cursor {
 void
 zfs_prep_opts(fsinfo_t *fsopts)
 {
-	zfs_opt_t *zfs = ecalloc(1, sizeof(*zfs));
+	size_t align;
+
+	align = alignof(uint64_t);
+	zfs_opt_t *zfs = aligned_alloc(align, roundup2(sizeof(*zfs), align));
+	if (zfs == NULL)
+		err(1, "aligned_alloc");
+	memset(zfs, 0, sizeof(*zfs));
 
 	const option_t zfs_options[] = {
 		{ '\0', "bootfs", &zfs->bootfs, OPT_STRPTR,
diff --git a/usr.sbin/makefs/zfs/zfs.h b/usr.sbin/makefs/zfs/zfs.h
index b92e2c03566..7ad3151dd8a 100644
--- a/usr.sbin/makefs/zfs/zfs.h
+++ b/usr.sbin/makefs/zfs/zfs.h
@@ -35,6 +35,7 @@
 #include <sys/queue.h>
 
 #include <bitstring.h>
+#include <stdalign.h>
 #include <stdbool.h>
 
 #include "makefs.h"
@@ -65,10 +66,13 @@ struct dataset_desc {
 };
 
 typedef struct {
-	bool		nowarn;
+	/*
+	 * Block buffer, needs to be aligned for various on-disk structures,
+	 * ZAPs, etc..
+	 */
+	char		filebuf[MAXBLOCKSIZE] __aligned(alignof(uint64_t));
 
-	/* I/O buffer, just for convenience. */
-	char		filebuf[MAXBLOCKSIZE];
+	bool		nowarn;
 
 	/* Pool parameters. */
 	const char	*poolname;