diff --git a/frontend/src/lib/document/transcription/useTranscriptionBlocks.svelte.test.ts b/frontend/src/lib/document/transcription/useTranscriptionBlocks.svelte.test.ts
index a7670791..dd837f48 100644
--- a/frontend/src/lib/document/transcription/useTranscriptionBlocks.svelte.test.ts
+++ b/frontend/src/lib/document/transcription/useTranscriptionBlocks.svelte.test.ts
@@ -259,12 +259,15 @@ describe('createTranscriptionBlocks.markAllReviewed', () => {
 		expect(ctrl.blocks.every((b) => b.reviewed)).toBe(true);
 	});
 
-	it('is a no-op when PUT returns non-OK', async () => {
+	it('throws and leaves blocks unchanged when PUT returns non-OK', async () => {
 		const fetchImpl = vi.fn(async (url: RequestInfo | URL, init?: RequestInit) => {
 			const u = url.toString();
 			const method = init?.method ?? 'GET';
 			if (u.includes('/review-all') && method === 'PUT') {
-				return new Response('', { status: 500 });
+				return new Response(JSON.stringify({ code: 'INTERNAL_ERROR' }), {
+					status: 500,
+					headers: { 'Content-Type': 'application/json' }
+				});
 			}
 			return new Response(JSON.stringify([baseBlock({ id: 'b-1', reviewed: false })]), {
 				status: 200,
@@ -274,7 +277,7 @@ describe('createTranscriptionBlocks.markAllReviewed', () => {
 
 		const ctrl = createTranscriptionBlocks({ documentId: () => 'doc-1', fetchImpl });
 		await ctrl.load();
-		await ctrl.markAllReviewed();
+		await expect(ctrl.markAllReviewed()).rejects.toThrow('INTERNAL_ERROR');
 		expect(ctrl.blocks[0].reviewed).toBe(false);
 	});
 });