diff --git a/apps/readest-app/src/__tests__/document/foliate-paginator-null-guards.test.ts b/apps/readest-app/src/__tests__/document/foliate-paginator-null-guards.test.ts
new file mode 100644
index 000000000..572a322c2
--- /dev/null
+++ b/apps/readest-app/src/__tests__/document/foliate-paginator-null-guards.test.ts
@@ -0,0 +1,39 @@
+import { describe, expect, it, vi } from 'vitest';
+
+import { getDirection } from 'foliate-js/paginator.js';
+
+// A view's iframe document is blank/detached while a section loads or the view
+// is torn down: body is null, and getComputedStyle(null) throws
+// "parameter 1 is not of type 'Element'" (READEST-2X).
+describe('getDirection null-document guard (READEST-2X)', () => {
+  it('falls back to horizontal-ltr instead of calling getComputedStyle(null)', () => {
+    const getComputedStyle = vi.fn((el: Element | null) => {
+      if (!el) {
+        throw new TypeError(
+          "Failed to execute 'getComputedStyle' on 'Window': parameter 1 is not of type 'Element'.",
+        );
+      }
+      return { writingMode: 'horizontal-tb', direction: 'ltr' } as CSSStyleDeclaration;
+    });
+    const doc = {
+      defaultView: { getComputedStyle },
+      body: null,
+      documentElement: { dir: '' },
+    } as unknown as Document;
+
+    expect(() => getDirection(doc)).not.toThrow();
+    expect(getDirection(doc)).toEqual({ vertical: false, rtl: false });
+    expect(getComputedStyle).not.toHaveBeenCalled();
+  });
+
+  it('still reads the writing mode from a present body', () => {
+    const getComputedStyle = vi.fn(() => ({ writingMode: 'vertical-rl', direction: 'ltr' }));
+    const doc = {
+      defaultView: { getComputedStyle },
+      body: { dir: '', querySelector: () => null },
+      documentElement: { dir: '' },
+    } as unknown as Document;
+
+    expect(getDirection(doc)).toEqual({ vertical: true, rtl: true });
+  });
+});
diff --git a/packages/foliate-js b/packages/foliate-js
index c1b1bbf6b..03cfb6c93 160000
--- a/packages/foliate-js
+++ b/packages/foliate-js
@@ -1 +1 @@
-Subproject commit c1b1bbf6b74a9d83f6acbefe3320529b13ea512b
+Subproject commit 03cfb6c9328e3d5705dd928debe4693effa5fbfc