diff --git a/core/tabs/utils/create-bootable-usb.sh b/core/tabs/utils/create-bootable-usb.sh
index 22defa25..01bee61f 100644
--- a/core/tabs/utils/create-bootable-usb.sh
+++ b/core/tabs/utils/create-bootable-usb.sh
@@ -233,7 +233,8 @@ write_iso(){
     printf "%b" "${RED}WARNING: This will erase all data on ${USB_DEVICE}. Are you sure you want to continue? (y/N): ${RC}"
     read -r CONFIRMATION
 
-    if [ "$(echo "$CONFIRMATION" | tr '[:upper:]' '[:lower:]')" != "yes" ] && [ "$(echo "$CONFIRMATION" | tr '[:upper:]' '[:lower:]')" != "y" ]; then
+    CONFIRMATION="$(echo "$CONFIRMATION" | tr '[:upper:]' '[:lower:]')"
+    if [ "${CONFIRMATION}" != "yes" ] && [ "${CONFIRMATION}" != "y" ]; then
         printf "%b\n" "${YELLOW}Operation cancelled.${RC}"
         exit 1
     fi