diff --git a/deploy-workbench.sh b/deploy-workbench.sh
index 9f1bcfc..ffa4cdc 100755
--- a/deploy-workbench.sh
+++ b/deploy-workbench.sh
@@ -189,8 +189,8 @@ create_persistence_partition() {
         rw_img_name="workbench_vfat.img"
         rw_img_path="${ISO_PATH}/staging/${rw_img_name}"
         if [ ! -f "${rw_img_path}" ] || [ "${DEBUG:-}" ] || [ "${FORCE:-}" ]; then
-                persistent_volume_size=100
-                ${SUDO} dd if=/dev/zero of="${rw_img_path}" bs=1M count=${persistent_volume_size}
+                persistent_volume_size_MB=100
+                ${SUDO} dd if=/dev/zero of="${rw_img_path}" bs=1M count=${persistent_volume_size_MB}
                 ${SUDO} mkfs.vfat "${rw_img_path}"
 
                 # generate structure on persistent partition