diff --git a/frontend/src/routes/admin/tags/[id]/page.svelte.test.ts b/frontend/src/routes/admin/tags/[id]/page.svelte.test.ts
index c52053bd..48a2e64f 100644
--- a/frontend/src/routes/admin/tags/[id]/page.svelte.test.ts
+++ b/frontend/src/routes/admin/tags/[id]/page.svelte.test.ts
@@ -143,11 +143,12 @@ describe('admin/tags/[id] page', () => {
 		expect(formSuccessBanner.length).toBe(0);
 	});
 
-	it('renders without throwing when mergeSuccess is null', async () => {
-		expect(() =>
-			render(AdminTagEditPage, {
-				props: { data: baseData({ mergeSuccess: null }), form: undefined }
-			})
-		).not.toThrow();
+	it('hides the merge-success banner when mergeSuccess is null', async () => {
+		render(AdminTagEditPage, {
+			props: { data: baseData({ mergeSuccess: null }), form: undefined }
+		});
+
+		// The merge-success banner has a distinct testid; mergeSuccess=null keeps it absent.
+		expect(document.querySelector('[data-testid="tag-merge-success"]')).toBeNull();
 	});
 });