diff --git a/nixos/tests/lomiri-gallery-app.nix b/nixos/tests/lomiri-gallery-app.nix
index b4e9c0bcfd7e..1f5638f39ba1 100644
--- a/nixos/tests/lomiri-gallery-app.nix
+++ b/nixos/tests/lomiri-gallery-app.nix
@@ -65,6 +65,7 @@ let
               systemPackages =
                 with pkgs;
                 [
+                  glib # Poke thumbnailer to process media via gdbus
                   mpv # URI dispatching for video support
                   xdotool # mouse movement
                 ]
@@ -78,7 +79,14 @@ let
               };
             };
 
-            i18n.supportedLocales = [ "all" ];
+            # Allow us to start thumbnailer ahead-of-time, hopefully let thumbnails get processed in peace
+            systemd.user.services."dbus-com.lomiri.Thumbnailer" = {
+              serviceConfig = {
+                Type = "dbus";
+                BusName = "com.lomiri.Thumbnailer";
+                ExecStart = "${pkgs.lomiri.lomiri-thumbnailer}/libexec/lomiri-thumbnailer/thumbnailer-service";
+              };
+            };
 
             fonts = {
               packages = with pkgs; [
@@ -97,6 +105,34 @@ let
             machine.succeed("mkdir /root/${builtins.dirOf file}")
             machine.succeed("cp -vr /etc/${imageDataDir}/${file} /root/${builtins.dirOf file}")
 
+            # Start thumbnailer, wait for idle shutdown
+            machine.systemctl("start dbus-com.lomiri.Thumbnailer", "root")
+            machine.wait_until_succeeds(
+                "env XDG_RUNTIME_DIR=/run/user/0 "
+                + "systemctl --user is-active dbus-com.lomiri.Thumbnailer"
+            )
+            machine.wait_for_console_text("thumbnail cache:")
+
+            # Request thumbnail processing, get initial thumbnail image into cache
+            # This can randomly take abit longer, just run it until it succeeds
+            # Touch file to invalidate failure cache
+            machine.wait_until_succeeds(
+                "touch '/root/${file}' && "
+                + "env XDG_RUNTIME_DIR=/run/user/0 "
+                + "gdbus call -e "
+                + "-d com.lomiri.Thumbnailer -o /com/lomiri/Thumbnailer "
+                + "-m com.lomiri.Thumbnailer.GetThumbnail "
+                + "'/root/${file}' "
+                # Same size as source, to reduce processing - we're very close to hitting 20s on slow hardware here
+                + "'@(ii) (500,500)'"
+            )
+
+            machine.wait_for_console_text("Idle timeout reached")
+            machine.wait_until_fails(
+                "env XDG_RUNTIME_DIR=/run/user/0 "
+                + "systemctl --user is-active dbus-com.lomiri.Thumbnailer"
+            )
+
             with subtest("lomiri gallery finds files"):
                 machine.succeed("lomiri-gallery-app >&2 &")
                 machine.wait_for_console_text("qq= AlbumsOverview") # logged when album page actually gets loaded
@@ -243,15 +279,13 @@ in
           machine.sleep(2)
 
           machine.wait_for_text("${imageLabel}") # make sure thumbnail processing worked
+          machine.screenshot("lomiri-gallery_mp4_thumbnail")
 
           machine.succeed("xdotool mousemove 510 380 click 1") # dispatch to system's video handler
           machine.wait_until_succeeds("pgrep -u root -f mpv") # wait for video to start
           machine.sleep(10)
           machine.succeed("pgrep -u root -f mpv") # should still be playing
           machine.screenshot("lomiri-gallery_mp4_dispatch")
-
-          machine.send_key("q")
-          machine.wait_until_fails("pgrep mpv") # wait for video to stop
     '';
   }
   {