diff --git a/web/hooks/use-users.ts b/web/hooks/use-users.ts
index 35244d73..5d2649b6 100644
--- a/web/hooks/use-users.ts
+++ b/web/hooks/use-users.ts
@@ -16,11 +16,13 @@ export const useUsers = () => {
   return users
 }
 
-export const useUserById = (userId: string) => {
+export const useUserById = (userId?: string) => {
   const [user, setUser] = useState<User | undefined>(undefined)
 
   useEffect(() => {
-    getUser(userId).then(setUser)
+    if (userId) {
+      getUser(userId).then(setUser)
+    }
   }, [userId])
 
   return user
diff --git a/web/pages/[username]/[contractSlug].tsx b/web/pages/[username]/[contractSlug].tsx
index 487942d5..7e7e6562 100644
--- a/web/pages/[username]/[contractSlug].tsx
+++ b/web/pages/[username]/[contractSlug].tsx
@@ -280,7 +280,7 @@ function ContractTopTrades(props: {
 
   // Now find the betId with the highest profit
   const topBetId = _.sortBy(bets, (b) => -profitById[b.id])[0]?.id
-  const topBettor = useUserById(betsById[topBetId].userId)
+  const topBettor = useUserById(betsById[topBetId]?.userId)
 
   // And also the commentId of the comment with the highest profit
   const topCommentId = _.sortBy(comments, (c) => -profitById[c.betId])[0]?.id