diff --git a/packages/webui/src/public/app.js b/packages/webui/src/public/app.js
index 1bd88cf2..78a1bf8d 100644
--- a/packages/webui/src/public/app.js
+++ b/packages/webui/src/public/app.js
@@ -41,7 +41,7 @@
     palette = p.id;
     if (!['system', 'light', 'dim', 'dark'].includes(mode)) mode = 'system';
     document.documentElement.dataset.palette = palette;
-    if (mode === 'system') delete document.documentElement.dataset.mode; else document.documentElement.dataset.mode = mode;
+    document.documentElement.dataset.mode = mode;
     $('palette').value = palette; $('mode').value = mode;
     try { localStorage.setItem('mosaic-console-appearance', JSON.stringify({ palette, mode })); } catch {}
   }