diff --git a/.changeset/fix-tweaks-local-themes.md b/.changeset/fix-tweaks-local-themes.md
new file mode 100644
index 000000000..51b8985fe
--- /dev/null
+++ b/.changeset/fix-tweaks-local-themes.md
@@ -0,0 +1,5 @@
+---
+default: patch
+---
+
+Fix tweaks not applying on built-in themes.
diff --git a/src/app/hooks/useTheme.ts b/src/app/hooks/useTheme.ts
index 7e3e04ee7..706fd6305 100755
--- a/src/app/hooks/useTheme.ts
+++ b/src/app/hooks/useTheme.ts
@@ -47,13 +47,13 @@ function makeRemoteTheme(url: string, kind: ThemeKind): Theme {
 export const LightTheme: Theme = {
   id: 'light-theme',
   kind: ThemeKind.Light,
-  classNames: ['light-theme', lightTheme, onLightFontWeight],
+  classNames: ['sable-remote-theme', 'light-theme', lightTheme, onLightFontWeight],
 };
 
 export const DarkTheme: Theme = {
   id: 'dark-theme',
   kind: ThemeKind.Dark,
-  classNames: ['dark-theme', darkTheme, onDarkFontWeight],
+  classNames: ['sable-remote-theme', 'dark-theme', darkTheme, onDarkFontWeight],
 };
 
 export const useThemes = (): Theme[] => {