diff --git a/src/proxmox-acme b/src/proxmox-acme
index 705f7df..18cbf20 100644
--- a/src/proxmox-acme
+++ b/src/proxmox-acme
@@ -510,7 +510,9 @@ _hex_dump() {
 }
 
 # stdin stdout
+#_url_encode [upper-hex]  the encoded hex will be upper-case if the argument upper-hex is followed
 _url_encode() {
+  _upper_hex=$1
   _hex_str=$(_hex_dump)
   for _hex_code in $_hex_str; do
     #upper case
@@ -720,6 +722,9 @@ _url_encode() {
 
       #other hex
       *)
+        if [ "$_upper_hex" = "upper-hex" ]; then
+          _hex_code=$(printf "%s" "$_hex_code" | _upper_case)
+        fi
         printf '%%%s' "$_hex_code"
         ;;
     esac