diff --git a/src/stores/__tests__/settings-store.test.ts b/src/stores/__tests__/settings-store.test.ts
index a9cb4780..992bbc6e 100644
--- a/src/stores/__tests__/settings-store.test.ts
+++ b/src/stores/__tests__/settings-store.test.ts
@@ -28,6 +28,13 @@ describe('settings-store', () => {
     });
   });
 
+  describe('week start', () => {
+    it('keeps a Saturday week start across a restart', () => {
+      expect(mergeWithDefaults({ calendarFirstDayOfWeek: 6 } as never).calendarFirstDayOfWeek).toBe(6);
+      expect(mergeWithDefaults({ calendarFirstDayOfWeek: 3 } as never).calendarFirstDayOfWeek).not.toBe(3);
+    });
+  });
+
   describe('mergeWithDefaults', () => {
     it('rejects values outside the allowed set', () => {
       const out = mergeWithDefaults({
diff --git a/src/stores/settings-store.ts b/src/stores/settings-store.ts
index 4403619e..0d4c1ac2 100644
--- a/src/stores/settings-store.ts
+++ b/src/stores/settings-store.ts
@@ -642,7 +642,7 @@ const VALIDATORS: Partial<Record<keyof PersistedSettings, (v: unknown) => boolea
   swipeMode: oneOf(['instant', 'reveal']),
   archiveMode: oneOf(['single', 'year', 'month']),
   calendarDefaultView: oneOf(['month', 'week', 'day', 'agenda']),
-  calendarFirstDayOfWeek: oneOf([0, 1]),
+  calendarFirstDayOfWeek: oneOf([0, 1, 6]),
   calendarTimeFormat: oneOf(['12h', '24h']),
   calendarHoverPreview: oneOf(['instant', 'delay-500ms', 'delay-1s', 'delay-2s', 'off']),
   filesFolderLayout: oneOf(['inline', 'sidebar']),