diff --git a/app/soapbox/features/ads/components/ad.tsx b/app/soapbox/features/ads/components/ad.tsx
index 871b76d067..5c1ff6a410 100644
--- a/app/soapbox/features/ads/components/ad.tsx
+++ b/app/soapbox/features/ads/components/ad.tsx
@@ -14,6 +14,7 @@ interface IAd {
   card: CardEntity,
   /** Impression URL to fetch upon display. */
   impression?: string,
+  /** Time when the ad expires and should no longer be displayed. */
   expires?: Date,
 }