diff --git a/bin/disk-image-create b/bin/disk-image-create
index 415cbaf9..943cf6c6 100755
--- a/bin/disk-image-create
+++ b/bin/disk-image-create
@@ -417,7 +417,7 @@ LOOPDEV=$(sudo losetup --show -f $TMP_IMAGE_PATH)
 export EXTRA_UNMOUNT="detach_loopback $LOOPDEV"
 export IMAGE_BLOCK_DEVICE=$LOOPDEV
 eval_run_d block-device "IMAGE_BLOCK_DEVICE="
-sudo mkfs $MKFS_OPTS -t $FS_TYPE -L ${DIB_ROOT_LABEL} ${IMAGE_BLOCK_DEVICE}
+sudo mkfs -t $FS_TYPE $MKFS_OPTS -L ${DIB_ROOT_LABEL} ${IMAGE_BLOCK_DEVICE}
 # Tuning the rootfs uuid works only for ext filesystems.
 if echo "$FS_TYPE" | grep -q "^ext"; then
     sudo tune2fs -U ${DIB_IMAGE_ROOT_FS_UUID} ${IMAGE_BLOCK_DEVICE}
diff --git a/doc/source/user_guide/building_an_image.rst b/doc/source/user_guide/building_an_image.rst
index 8137fd00..16dccc11 100644
--- a/doc/source/user_guide/building_an_image.rst
+++ b/doc/source/user_guide/building_an_image.rst
@@ -58,18 +58,25 @@ formats are:
 Filesystem Caveat
 -----------------
 
-By default, disk-image-create uses a 4k byte-to-inode ratio when creating the
-filesystem in the image. This allows large 'whole-system' images to utilize
-several TB disks without exhausting inodes. In contrast, when creating images
-intended for tenant instances, this ratio consumes more disk space than an
-end-user would expect (e.g. a 50GB root disk has 47GB avail.). If the image is
-intended to run within a tens to hundrededs of gigabyte disk, setting the
-byte-to-inode ratio to the ext4 default of 16k will allow for more usable space
-on the instance. The default can be overridden by passing --mkfs-options like
-this::
+By default, disk-image-create uses a 4k byte-to-inode ratio when
+creating the filesystem in the image. This allows large 'whole-system'
+images to utilize several TB disks without exhausting inodes. In
+contrast, when creating images intended for tenant instances, this
+ratio consumes more disk space than an end-user would expect (e.g. a
+50GB root disk has 47GB avail.). If the image is intended to run
+within a tens to hundrededs of gigabyte disk, setting the
+byte-to-inode ratio to the ext4 default of 16k will allow for more
+usable space on the instance. The default can be overridden by passing
+``--mkfs-options`` like this::
 
     disk-image-create --mkfs-options '-i 16384' <distro> vm
 
+You can also select a different filesystem by setting the ``FS_TYPE``
+environment variable.
+
+Note ``--mkfs-options`` are options passed to the mfks *driver*,
+rather than ``mkfs`` itself (i.e. after the initial `-t` argument).
+
 Speedups
 --------
 If you have 4GB of available physical RAM (as reported by /proc/meminfo