diff --git a/schema.graphql b/schema.graphql
index f0f25b7..bb4f171 100644
--- a/schema.graphql
+++ b/schema.graphql
@@ -25,7 +25,7 @@ type Receiver @entity {
   transactions: [Transaction!] @derivedFrom(field: "receiver")
 }
 
-type Transaction @entity{
+type Transaction @entity(immutable: true){
   id: Bytes!
   transactionGroupID: Bytes!
   type: String!