diff --git a/setup/start/cloudron-firewall.sh b/setup/start/cloudron-firewall.sh
index e88d64171..b62b38186 100755
--- a/setup/start/cloudron-firewall.sh
+++ b/setup/start/cloudron-firewall.sh
@@ -15,7 +15,7 @@ iptables -A CLOUDRON -p tcp -m tcp -m multiport --dports 22,25,80,202,443,587,99
 # turn and stun service
 iptables -t filter -A CLOUDRON -p tcp -m multiport --dports 3478,5349 -j ACCEPT
 iptables -t filter -A CLOUDRON -p udp -m multiport --dports 3478,5349 -j ACCEPT
-iptables -t filter -A CLOUDRON -p udp -m multiport --dports 50000-51000 -j ACCEPT
+iptables -t filter -A CLOUDRON -p udp -m multiport --dports 50000:51000 -j ACCEPT
 
 iptables -t filter -A CLOUDRON -p icmp --icmp-type echo-request -j ACCEPT
 iptables -t filter -A CLOUDRON -p icmp --icmp-type echo-reply -j ACCEPT