diff --git a/nixos/modules/monitoring/server/prometheus.nix b/nixos/modules/monitoring/server/prometheus.nix
index c92261ccad2ebdd8dd34dda9027e66962b345be9..1f27f023df5b3211a81e3603226cc7cfe2c25e27 100644
--- a/nixos/modules/monitoring/server/prometheus.nix
+++ b/nixos/modules/monitoring/server/prometheus.nix
@@ -59,7 +59,9 @@ in {
           scheme = "https";
           tls_config.insecure_skip_verify = true;
           static_configs = [{
-            targets = cfg.paymentExporterTargets;
+            # Explicitly setting the port number so the relabel_config can filter it out again.
+            # Leaving it out makes the port number show in Grafana.
+            targets = map (x: x + ":443") cfg.paymentExporterTargets;
           }];
           relabel_configs = [ dropPortNumber ];
         }