diff --git a/mail-server/assertions.nix b/mail-server/assertions.nix
index 2b4b262..0e5b15b 100644
--- a/mail-server/assertions.nix
+++ b/mail-server/assertions.nix
@@ -13,7 +13,7 @@
       assertion = config.mailserver.forwards == {};
       message = "When the LDAP support is enable (mailserver.ldap.enable = true), it is not possible to define mailserver.forwards";
     }
-  ] ++ lib.optionals (config.mailserver.certificateScheme != "acme") [
+  ] ++ lib.optionals (config.mailserver.enable && config.mailserver.certificateScheme != "acme") [
     {
       assertion = config.mailserver.acmeCertificateName == config.mailserver.fqdn;
       message = "When the certificate scheme is not 'acme' (mailserver.certificateScheme != \"acme\"), it is not possible to define mailserver.acmeCertificateName";