diff --git a/nixos/modules/config/xdg/portal.nix b/nixos/modules/config/xdg/portal.nix
index 4e85bf794da..89ddf80b575 100644
--- a/nixos/modules/config/xdg/portal.nix
+++ b/nixos/modules/config/xdg/portal.nix
@@ -1,10 +1,12 @@
 { config, pkgs ,lib ,... }:
+
 with lib;
+
 {
   options.xdg.portal = {
     enable =
       mkEnableOption "<link xlink:href='https://github.com/flatpak/xdg-desktop-portal'>xdg desktop integration</link>"//{
-        default = config.services.xserver.enable;
+        default = false;
       };
 
     extraPortals = mkOption {
@@ -19,6 +21,17 @@ with lib;
         environments you probably want to add them yourself.
       '';
     };
+
+    gtkUsePortal = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Sets environment variable <literal>GTK_USE_PORTAL</literal> to <literal>1</literal>.
+        This is needed for packages ran outside Flatpak to respect and use XDG Desktop Portals.
+        For example, you'd need to set this for non-flatpak Firefox to use native filechoosers.
+        Defaults to <literal>false</literal> to respect its opt-in nature.
+      '';
+    };
   };
 
   config =
@@ -28,10 +41,17 @@ with lib;
 
     in mkIf cfg.enable {
 
+      assertions = [
+        { assertion = (cfg.gtkUsePortal -> cfg.extraPortals != []);
+          message = "Setting xdg.portal.gtkUsePortal to true requires a portal implementation in xdg.portal.extraPortals such as xdg-desktop-portal-gtk or xdg-desktop-portal-kde.";
+        }
+      ];
+
       services.dbus.packages  = packages;
       systemd.packages = packages;
+
       environment.variables = {
-        GTK_USE_PORTAL = "1";
+        GTK_USE_PORTAL = optional cfg.gtkUsePortal "1";
         XDG_DESKTOP_PORTAL_PATH = map (p: "${p}/share/xdg-desktop-portal/portals") cfg.extraPortals;
       };
     };
diff --git a/nixos/modules/services/desktops/flatpak.nix b/nixos/modules/services/desktops/flatpak.nix
index 82463406118..1492d855aa0 100644
--- a/nixos/modules/services/desktops/flatpak.nix
+++ b/nixos/modules/services/desktops/flatpak.nix
@@ -22,6 +22,12 @@ in {
   ###### implementation
   config = mkIf cfg.enable {
 
+    assertions = [
+      { assertion = (config.xdg.portal.enable == true);
+        message = "To use Flatpak you must enable XDG Desktop Portals with xdg.portal.enable.";
+      }
+    ];
+
     environment.systemPackages = [ pkgs.flatpak ];
 
     services.dbus.packages = [ pkgs.flatpak ];
diff --git a/nixos/modules/services/x11/desktop-managers/gnome3.nix b/nixos/modules/services/x11/desktop-managers/gnome3.nix
index c4c742ed9d7..cd750242125 100644
--- a/nixos/modules/services/x11/desktop-managers/gnome3.nix
+++ b/nixos/modules/services/x11/desktop-managers/gnome3.nix
@@ -154,6 +154,7 @@ in {
     services.hardware.bolt.enable = mkDefault true;
     services.xserver.libinput.enable = mkDefault true; # for controlling touchpad settings via gnome control center
     systemd.packages = [ pkgs.gnome3.vino ];
+    xdg.portal.enable = true;
     xdg.portal.extraPortals = [ pkgs.xdg-desktop-portal-gtk ];
 
     # If gnome3 is installed, build vim for gtk3 too.
diff --git a/nixos/modules/services/x11/desktop-managers/plasma5.nix b/nixos/modules/services/x11/desktop-managers/plasma5.nix
index 98c9ae86cee..6d148fba895 100644
--- a/nixos/modules/services/x11/desktop-managers/plasma5.nix
+++ b/nixos/modules/services/x11/desktop-managers/plasma5.nix
@@ -170,7 +170,7 @@ in
 
           xdg-user-dirs # Update user dirs as described in https://freedesktop.org/wiki/Software/xdg-user-dirs/
         ]
-        
+
         # Phonon audio backend
         ++ lib.optional (cfg.phononBackend == "gstreamer") libsForQt5.phonon-backend-gstreamer
         ++ lib.optional (cfg.phononBackend == "gstreamer" && cfg.enableQt4Support) pkgs.phonon-backend-gstreamer
@@ -233,6 +233,7 @@ in
       security.pam.services.sddm.enableKwallet = true;
       security.pam.services.slim.enableKwallet = true;
 
+      xdg.portal.enable = true;
       xdg.portal.extraPortals = [ pkgs.xdg-desktop-portal-kde ];
 
       # Update the start menu for each user that is currently logged in