diff --git a/apps/portal-bff/src/structures/structure-kind.spec.ts b/apps/portal-bff/src/structures/structure-kind.spec.ts
index 55e21e9..6745e42 100644
--- a/apps/portal-bff/src/structures/structure-kind.spec.ts
+++ b/apps/portal-bff/src/structures/structure-kind.spec.ts
@@ -35,7 +35,10 @@ describe('isStructureKind', () => {
   });
 
   it('narrows the type at the call site', () => {
-    const candidate: string = 'medico_social';
+    // Round-trip through `String()` to widen the literal to `string`.
+    // Without this the inferred type is `'medico_social'`, already a
+    // StructureKind subtype — the narrowing check would be vacuous.
+    const candidate = String('medico_social');
     if (!isStructureKind(candidate)) {
       throw new Error('unreachable — candidate is a known kind');
     }