diff --git a/quickemu b/quickemu
index 740fb7d..9ada4f5 100755
--- a/quickemu
+++ b/quickemu
@@ -161,7 +161,7 @@ function vm_boot() {
       exit 1
     else
       disk_curr_size=$(stat -c%s "${disk_img}")
-      if [ ${disk_curr_size} -le ${disk_min_size} ]; then
+      if [ ${disk_curr_size} -le ${DISK_MIN_SIZE} ]; then
         echo "             Looks unused, booting from ${iso}"
         if [ -z "${iso}" ]; then
           echo "ERROR! You haven't specified a .iso image to boot from."
@@ -316,13 +316,13 @@ iso=""
 driver_iso=""
 disk_img=""
 disk=""
-disk_min_size=$((197632 * 8))
 DELETE=0
 ENABLE_EFI=0
 SNAPSHOT_ACTION=""
 SNAPSHOT_TAG=""
 STATUSQUO=""
 VM=""
+readonly DISK_MIN_SIZE=$((197632 * 8))
 readonly QEMU="/snap/bin/qemu-virgil"
 readonly QEMU_IMG="/snap/bin/qemu-virgil.qemu-img"
 readonly LAUNCHER=$(basename $0)