diff --git a/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/model/RetrievedAccountData.kt b/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/model/RetrievedAccountData.kt
index 2c15a132..be9195ed 100644
--- a/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/model/RetrievedAccountData.kt
+++ b/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/model/RetrievedAccountData.kt
@@ -9,7 +9,7 @@ open class RetrievedAccountData(
 ) {
 
     open fun addBookedTransactions(transactions: List<AccountTransaction>) {
-        val bookedTransactions = this.bookedTransactions.toMutableList() // some banks like Postbank return some transactions multiple times -> remove these
+        val bookedTransactions = this.bookedTransactions.toMutableSet() // some banks like Postbank return some transactions multiple times -> remove these
 
         bookedTransactions.addAll(transactions)