diff --git a/nixos/modules/services/monitoring/prometheus/default.nix b/nixos/modules/services/monitoring/prometheus/default.nix
index c64ab448e0e..cbd4cc452a7 100644
--- a/nixos/modules/services/monitoring/prometheus/default.nix
+++ b/nixos/modules/services/monitoring/prometheus/default.nix
@@ -490,7 +490,7 @@ in {
     };
 
     port = mkOption {
-      type = types.int;
+      type = types.port;
       default = 9090;
       description = ''
         Port to listen on.