diff --git a/create-training-box.sh b/create-training-box.sh
index 76901ec..a3494a6 100755
--- a/create-training-box.sh
+++ b/create-training-box.sh
@@ -2,22 +2,33 @@
 
 set -e
 
-VMDK=upstream-training-disk001.vmdk
+# Create a VMDK image by default. Override with
+# "create-training-box.sh <FORMAT>", where FORMAT can be any format
+# that qemu-img understands.
+FORMAT=${1:-vmdk}
+DISK=upstream-training-disk001.$FORMAT
+
 export ELEMENTS_PATH=./elements/
 
 mkdir -p tmp
 
+DIB_OPTIONS="-o tmp/$DISK -t $FORMAT --image-size 40"
+if [ "$FORMAT" = "vmdk" ]; then
+    DIB_OPTIONS="$DIB_OPTIONS --qemu-img-options subformat=streamOptimized"
+fi
+
 disk-image-create \
-    -o "tmp/$VMDK" \
-    -t vmdk \
-    --qemu-img-options subformat=streamOptimized \
-    --image-size 40 \
+    $DIB_OPTIONS \
     upstream-training
 
-DIST="dist/upstream-training-$(date +%Y%m%d-%H%M).ova"
+# If we're configured to create a VMDK or VDI image, assume that we're
+# building for VirtualBox and also create an OVA tarball
+if [ "$FORMAT" = "vmdk" ] || [ "$FORMAT" = "vdi" ]; then
+    DIST="dist/upstream-training-$(date +%Y%m%d-%H%M).ova"
 
-cp upstream-training.ovf tmp/
+    cp upstream-training.ovf tmp/
 
-pushd tmp/
-tar -cf "../$DIST" upstream-training.ovf "$VMDK"
-popd
+    pushd tmp/
+    tar -cf "../$DIST" upstream-training.ovf "$DISK"
+    popd
+fi