diff --git a/dovecot.nix b/dovecot.nix
index a379ad5..e112293 100644
--- a/dovecot.nix
+++ b/dovecot.nix
@@ -168,7 +168,7 @@ in {
         description = "Host to which spam/ham will be forwarded.";
       };
       port = mkOption {
-        type = str;
+        type = port;
         description = "Port to which spam/ham will be forwarded.";
       };
     };
@@ -259,8 +259,9 @@ in {
               pkgs.writeShellApplication {
                 name = "rspamd_${msg}";
                 runtimeInputs = with pkgs; [ rspamd ];
-                text =
-                  "exec rspamc -h ${cfg.rspamd.host}:${cfg.rspamd.port} ${msg}";
+                text = "exec rspamc -h ${cfg.rspamd.host}:${
+                    toString cfg.rspamd.port
+                  } ${msg}";
               };
             learnHam = teachRspamd "learn_ham";
             learnSpam = teachRspamd "learn_spam";