diff --git a/nixos/modules/services/mail/postfix.nix b/nixos/modules/services/mail/postfix.nix
index b84c63e6421..839da7407ef 100644
--- a/nixos/modules/services/mail/postfix.nix
+++ b/nixos/modules/services/mail/postfix.nix
@@ -265,7 +265,7 @@ in
       extraAliases = mkOption {
         default = "";
         description = "
-          Additional entries to put verbatim into aliases file.
+          Additional entries to put verbatim into aliases file, cf. man-page aliases(8).
         ";
       };
 
@@ -302,7 +302,7 @@ in
       virtual = mkOption {
         default = "";
         description = "
-          Entries for the virtual alias map.
+          Entries for the virtual alias map, cf. man-page virtual(8).
         ";
       };