diff --git a/clonedisk.sh b/clonedisk.sh
index 9e5ea74..dcfae9e 100755
--- a/clonedisk.sh
+++ b/clonedisk.sh
@@ -133,7 +133,7 @@ if [[ ${OUT#/dev/nvme} != $OUT ]]; then
     OUT="${OUT}p"
 fi
 
-dd if=${IN}2 of=${OUT}2 status=progress
+dd bs=4096 if=${IN}2 of=${OUT}2 status=progress
 sfdisk --part-uuid ${OUT_DEV} 2 $(blkid -o value -s PARTUUID ${IN}2)
 
 if ! [[ $UPDATE ]]; then
diff --git a/mkimage.sh b/mkimage.sh
index 57e2a0a..bfab9da 100755
--- a/mkimage.sh
+++ b/mkimage.sh
@@ -182,7 +182,7 @@ umount "$MY_TMPDIR"/boot
 
 # ------------------------------------------------------------------------------
 # root1
-dd if="$SOURCE"/root.img of=${DEV_PART}2 status=progress
+dd bs=4096 if="$SOURCE"/root.img of=${DEV_PART}2 status=progress
 
 # ------------------------------------------------------------------------------
 # data
diff --git a/update.sh b/update.sh
index a3725f3..58ed766 100755
--- a/update.sh
+++ b/update.sh
@@ -199,7 +199,9 @@ if [[ ${FILES["update.sh"]} ]] && [[ -e ./update.sh ]]; then
  exit $?
 fi
 
-dd status=progress if=root.img of=${ROOT_DEV}-part${NEW_ROOT_PARTNO}
+dd bs=4096 conv=fsync status=progress \
+    if=root.img \
+    of=${ROOT_DEV}-part${NEW_ROOT_PARTNO}
 
 # set the new partition uuids
 ROOT_UUID=${ROOT_HASH:32:8}-${ROOT_HASH:40:4}-${ROOT_HASH:44:4}-${ROOT_HASH:48:4}-${ROOT_HASH:52:12}