diff --git a/nix/module.nix b/nix/module.nix
index eab3c23..fee9fe2 100644
--- a/nix/module.nix
+++ b/nix/module.nix
@@ -159,7 +159,7 @@ in
         "*.demo.archtika.com" = {
           enableACME = true;
           forceSSL = true;
-          serverName = "~^(?<subdomain>.+)\.demo\.archtika\.com$";
+          serverName = "~^(?<subdomain>.+)\\.demo\\.archtika\\.com$";
           locations = {
             "/" = {
               alias = "/var/www/archtika-websites/$subdomain/";