diff --git a/node/src/main/kotlin/net/corda/node/services/persistence/DBTransactionMappingStorage.kt b/node/src/main/kotlin/net/corda/node/services/persistence/DBTransactionMappingStorage.kt
index 3ed86c65af..e81c6767f8 100644
--- a/node/src/main/kotlin/net/corda/node/services/persistence/DBTransactionMappingStorage.kt
+++ b/node/src/main/kotlin/net/corda/node/services/persistence/DBTransactionMappingStorage.kt
@@ -55,7 +55,7 @@ class DBTransactionMappingStorage : StateMachineRecordedTransactionMappingStorag
     val updates: PublishSubject<StateMachineTransactionMapping> = PublishSubject.create()
 
     override fun addMapping(stateMachineRunId: StateMachineRunId, transactionId: SecureHash) {
-        stateMachineTransactionMap[transactionId] = stateMachineRunId
+        stateMachineTransactionMap.addWithDuplicatesAllowed(transactionId, stateMachineRunId)
         updates.bufferUntilDatabaseCommit().onNext(StateMachineTransactionMapping(stateMachineRunId, transactionId))
     }