diff --git a/openvpn-install.sh b/openvpn-install.sh
index ee420ca..62c5642 100644
--- a/openvpn-install.sh
+++ b/openvpn-install.sh
@@ -110,6 +110,18 @@ if [[ -e /etc/openvpn/server.conf ]]; then
 			else
 				read -p "Select one client [1-$NUMBEROFCLIENTS]: " CLIENTNUMBER
 			fi
+			#check if selected client does exist
+			if [[ !("$CLIENTNUMBER" =~ ^[0-9]+$) ]]; then
+				echo ""
+				echo "error: please enter a valid number!" 
+				exit
+			fi
+			if [[ "$CLIENTNUMBER" < "1" || "$CLIENTNUMBER" > "$NUMBEROFCLIENTS" || ${#CLIENTNUMBER} != ${#NUMBEROFCLIENTS} ]]; then
+				echo ""
+				echo "error: could not find client number $CLIENTNUMBER."
+				exit
+			fi
+			echo "INPUT: $CLIENTNUMBER"
 			CLIENT=$(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/
 			./easyrsa --batch revoke $CLIENT
@@ -422,4 +434,4 @@ verb 3" > /etc/openvpn/client-common.txt
 	echo ""
 	echo "Your client configuration is available at" ~/"$CLIENT.ovpn"
 	echo "If you want to add more clients, you simply need to run this script again!"
-fi
\ No newline at end of file
+fi