diff --git a/apps/frontend/app/problem/[problemId]/submission/_components/Columns.tsx b/apps/frontend/app/problem/[problemId]/submission/_components/Columns.tsx
index b75bd9df9c..86e20c3ecc 100644
--- a/apps/frontend/app/problem/[problemId]/submission/_components/Columns.tsx
+++ b/apps/frontend/app/problem/[problemId]/submission/_components/Columns.tsx
@@ -13,7 +13,7 @@ export const columns: ColumnDef<SubmissionItem>[] = [
   {
     header: () => 'User ID',
     accessorKey: 'username',
-    cell: ({ row }) => row.original.user.username
+    cell: ({ row }) => row.original.user?.username ?? 'Unknown User'
   },
   {
     header: () => 'Result',