diff --git a/nextjs-app/lib/utils.ts b/nextjs-app/lib/utils.ts
index 18fdd10..330cc88 100644
--- a/nextjs-app/lib/utils.ts
+++ b/nextjs-app/lib/utils.ts
@@ -588,7 +588,7 @@ export interface OfstedListBadge {
  *   - No inspection: "Not yet inspected" in grey
  */
 export function buildOfstedListBadge(school: {
-  ofsted_grade?: number | null;
+  ofsted_grade?: 1 | 2 | 3 | 4 | null;
   ofsted_date?: string | null;
   ofsted_framework?: string | null;
 }): OfstedListBadge {