diff --git a/nixos/modules/services/x11/display-managers/slim.nix b/nixos/modules/services/x11/display-managers/slim.nix
index 9ee4e0dc7cb0..c7fbfa85e335 100644
--- a/nixos/modules/services/x11/display-managers/slim.nix
+++ b/nixos/modules/services/x11/display-managers/slim.nix
@@ -19,6 +19,7 @@ let
       reboot_cmd ${config.systemd.package}/sbin/shutdown -r now
       ${optionalString (cfg.defaultUser != null) ("default_user " + cfg.defaultUser)}
       ${optionalString cfg.autoLogin "auto_login yes"}
+      ${cfg.extraConfig}
     '';
 
   # Unpack the SLiM theme, or use the default.
@@ -89,6 +90,15 @@ in
         '';
       };
 
+      extraConfig = mkOption {
+        type = types.lines;
+        default = "";
+        description = ''
+          Extra configuration options for SLiM login manager. Do not
+          add options that can be configured directly.
+        '';
+      };
+
     };
 
   };