diff --git a/src/incentive-details.ts b/src/incentive-details.ts
index 6500c08..b0dc188 100644
--- a/src/incentive-details.ts
+++ b/src/incentive-details.ts
@@ -96,6 +96,9 @@ function formatStartDate(start_date: number, type: IncentiveType) {
     } else {
       return html`${start_date.toString()}`;
     }
+  } else {
+    // while we technically don't expect another IncentiveType, fall back to date here if needed:
+    return html`${start_date.toString()}`;
   }
 }