diff --git a/frontend/src/lib/ocr/translateOcrProgress.spec.ts b/frontend/src/lib/ocr/translateOcrProgress.spec.ts
index e0114aaf..576fc425 100644
--- a/frontend/src/lib/ocr/translateOcrProgress.spec.ts
+++ b/frontend/src/lib/ocr/translateOcrProgress.spec.ts
@@ -77,6 +77,12 @@ describe('translateOcrProgress', () => {
 		expect(result.totalPages).toBe(10);
 	});
 
+	it('PREPROCESSING_PAGE with no colon parts gracefully falls back to zero', () => {
+		const result = translateOcrProgress('PREPROCESSING_PAGE');
+		expect(result.currentPage).toBe(0);
+		expect(result.totalPages).toBe(0);
+	});
+
 	it('translates ERROR', () => {
 		expect(translateOcrProgress('ERROR').message).toBe('OCR fehlgeschlagen');
 	});