diff --git a/nixos/modules/services/x11/xserver.nix b/nixos/modules/services/x11/xserver.nix
index eb8c4c17e98..e89ad9a5796 100644
--- a/nixos/modules/services/x11/xserver.nix
+++ b/nixos/modules/services/x11/xserver.nix
@@ -441,6 +441,7 @@ in
 
       serverFlagsSection = mkOption {
         default = "";
+        type = types.lines;
         example =
           ''
           Option "BlankTime" "0"