diff --git a/services/prometheus-node.nix b/services/prometheus-node.nix
index 17ea974..ddb9672 100644
--- a/services/prometheus-node.nix
+++ b/services/prometheus-node.nix
@@ -5,8 +5,8 @@
     enable = true;
     #listenAddress = "0.0.0.0";
     firewallRules = ''
-      ip saddr 195.160.173.14/32 tcp dport ${config.services.prometheus.exporters.node.port} accept comment "Allow prometheus on monitoring.berlin.ccc.der"
-      ip6 saddr 2001:678:760:cccb::14/128 tcp dport ${config.services.prometheus.exporters.node.port} accept comment "Allow prometheus on monitoring.berlin.ccc.der"
+      ip saddr 195.160.173.14/32 tcp dport ${toString config.services.prometheus.exporters.node.port} accept comment "Allow prometheus on monitoring.berlin.ccc.der"
+      ip6 saddr 2001:678:760:cccb::14/128 tcp dport ${toString config.services.prometheus.exporters.node.port} accept comment "Allow prometheus on monitoring.berlin.ccc.der"
     '';
     enabledCollectors = [];
     disabledCollectors = [];