diff --git a/mail-server/networking.nix b/mail-server/networking.nix
index 851a1f0..f9b3336 100644
--- a/mail-server/networking.nix
+++ b/mail-server/networking.nix
@@ -24,10 +24,10 @@ in
 
     networking.firewall = {
       allowedTCPPorts = [ 25 587 ]
-        ++ (if enableImap then [ 143 ] else [])
-        ++ (if enableImapSsl then [ 993 ] else [])
-        ++ (if enablePop3 then [ 110 ] else [])
-        ++ (if enablePop3Ssl then [ 995 ] else []);
+        ++ lib.optional enableImap 143
+        ++ lib.optional enableImapSsl 993
+        ++ lib.optional enablePop3 110
+        ++ lib.optional enablePop3Ssl 995;
     };
   };
 }