diff --git a/README.md b/README.md
index 23a3957..9f75d6f 100644
--- a/README.md
+++ b/README.md
@@ -91,6 +91,18 @@ export PASS="1"
 ./openvpn-install.sh
 ```
 
+### Headless User Removal
+
+The removal of an existing user can also be fully automated. Again, the key is to provide the (string) value of the `MENU_OPTION` variable along with the remaining mandatory variables before invoking the script.
+
+The following Bash script removes the existing user `bar` from an OpenVPN configuration
+```bash
+#!/bin/bash
+export MENU_OPTION="2"
+export CLIENT="bar"
+./openvpn-install.sh
+```
+
 ## Features
 
 - Installs and configures a ready-to-use OpenVPN server
diff --git a/openvpn-install.sh b/openvpn-install.sh
index 685f607..3e2e8ab 100755
--- a/openvpn-install.sh
+++ b/openvpn-install.sh
@@ -1144,14 +1144,16 @@ function revokeClient() {
 	echo ""
 	echo "Select the existing client certificate you want to revoke"
 	tail -n +2 /etc/openvpn/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | nl -s ') '
-	until [[ $CLIENTNUMBER -ge 1 && $CLIENTNUMBER -le $NUMBEROFCLIENTS ]]; do
-		if [[ $CLIENTNUMBER == '1' ]]; then
-			read -rp "Select one client [1]: " CLIENTNUMBER
-		else
-			read -rp "Select one client [1-$NUMBEROFCLIENTS]: " CLIENTNUMBER
-		fi
+	until [[ "$CLIENT" =~ ^[a-zA-Z0-9_]+$ ]]; do
+		until [[ $CLIENTNUMBER -ge 1 && $CLIENTNUMBER -le $NUMBEROFCLIENTS ]]; do
+			if [[ $CLIENTNUMBER == '1' ]]; then
+				read -rp "Select one client [1]: " CLIENTNUMBER
+			else
+				read -rp "Select one client [1-$NUMBEROFCLIENTS]: " CLIENTNUMBER
+			fi
+		done
+		CLIENT=$(tail -n +2 /etc/openvpn/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | sed -n "$CLIENTNUMBER"p)
 	done
-	CLIENT=$(tail -n +2 /etc/openvpn/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | sed -n "$CLIENTNUMBER"p)
 	cd /etc/openvpn/easy-rsa/ || return
 	./easyrsa --batch revoke "$CLIENT"
 	EASYRSA_CRL_DAYS=3650 ./easyrsa gen-crl