diff --git a/nixos/modules/services/x11/desktop-managers/xfce.nix b/nixos/modules/services/x11/desktop-managers/xfce.nix
index 4c4e3d96798..634d2a39576 100644
--- a/nixos/modules/services/x11/desktop-managers/xfce.nix
+++ b/nixos/modules/services/x11/desktop-managers/xfce.nix
@@ -33,6 +33,14 @@ in
         default = false;
         description = "Don't install XFCE desktop components (xfdesktop, panel and notification daemon).";
       };
+
+      extraSessionCommands = mkOption {
+        default = "";
+        type = types.lines;
+        description = ''
+          Shell commands executed just before XFCE is started.
+        '';
+      };
     };
 
   };
@@ -45,6 +53,8 @@ in
         bgSupport = true;
         start =
           ''
+            ${cfg.extraSessionCommands}
+
             # Set GTK_PATH so that GTK+ can find the theme engines.
             export GTK_PATH="${config.system.path}/lib/gtk-2.0:${config.system.path}/lib/gtk-3.0"
 
diff --git a/nixos/modules/services/x11/window-managers/i3.nix b/nixos/modules/services/x11/window-managers/i3.nix
index aea0a898678..cfe9439b688 100644
--- a/nixos/modules/services/x11/window-managers/i3.nix
+++ b/nixos/modules/services/x11/window-managers/i3.nix
@@ -15,12 +15,21 @@ let
         If left at the default value, $HOME/.i3/config will be used.
       '';
     };
+    extraSessionCommands = mkOption {
+      default = "";
+      type = types.lines;
+      description = ''
+        Shell commands executed just before i3 is started.
+      '';
+    };
   };
 
   i3config = name: pkg: cfg: {
     services.xserver.windowManager.session = [{
       inherit name;
       start = ''
+        ${cfg.extraSessionCommands}
+
         ${pkg}/bin/i3 ${optionalString (cfg.configFile != null)
           "-c \"${cfg.configFile}\""
         } &