diff --git a/config/mail.scm b/config/mail.scm
index 48a6f28..7d7f28c 100644
--- a/config/mail.scm
+++ b/config/mail.scm
@@ -8,14 +8,14 @@
 
 (define* (opensmtpd-config #:key interface domain aliases dkim-selector)
   (define (format-aliases aliases)
-    (string-append (format #f "~:{~a: ~a\n~}\n"
-                           (cons* '("MAILER-DAEMON" "postmaster")
-                                  '("postmaster" "root")
-                                  '("hostmaster" "root")
-                                  '("webmaster" "root")
-                                  '("abuse" "root")
-                                  '("security" "root")
-                                  aliases))))
+    (format #f "~:{~a: ~a\n~}\n"
+            (cons* '("MAILER-DAEMON" "postmaster")
+                   '("postmaster" "root")
+                   '("hostmaster" "root")
+                   '("webmaster" "root")
+                   '("abuse" "root")
+                   '("security" "root")
+                   aliases)))
 
   (mixed-text-file "smtpd.conf" "\
 smtp max-message-size \"1G\"