diff --git a/modules/mailserver/default.nix b/modules/mailserver/default.nix
index 1e27c48..66a52c2 100644
--- a/modules/mailserver/default.nix
+++ b/modules/mailserver/default.nix
@@ -36,7 +36,7 @@ with lib;
         extraVirtualAliases = {
           "postmaster@ens.school" = "julien.malka@ens.school";
         };
-        certificateScheme = 3;
+        certificateScheme = "acme-nginx";
       };
 
       services.roundcube = {