diff --git a/hosts/monitoring/prometheus.nix b/hosts/monitoring/prometheus.nix
index a0c9b58..0adb80b 100644
--- a/hosts/monitoring/prometheus.nix
+++ b/hosts/monitoring/prometheus.nix
@@ -53,7 +53,7 @@
       {
         job_name = "postgres";
         scrape_interval = "15s";
-        static_configs = [{ targets = [ "sql.berlin.ccc.de:${config.services.prometheus.exporters.postgres.port}" ]; }];
+        static_configs = [{ targets = [ "sql.berlin.ccc.de:${toString config.services.prometheus.exporters.postgres.port}" ]; }];
       }
     ];
     ruleFiles = [