diff --git a/backend/prisma/schema.prisma b/backend/prisma/schema.prisma
index 619b9fa..c6ff654 100644
--- a/backend/prisma/schema.prisma
+++ b/backend/prisma/schema.prisma
@@ -51,7 +51,7 @@ model Transaction {
   watchEvent   WatchEvent? @relation(fields: [watchEventId], references: [id])
   
   // For spent transactions
-  requestId   String? @map("request_id")
+  requestId   String? @unique @map("request_id")
   request     ContentRequest? @relation(fields: [requestId], references: [id])
   
   // Solana transaction reference