diff --git a/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsClient.kt b/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsClient.kt
index 0589e34d..0c6dcfc0 100644
--- a/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsClient.kt
+++ b/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsClient.kt
@@ -17,7 +17,7 @@ import net.dankito.utils.multiplatform.Date
  * [addAccountAsync] gets user's TAN methods, user's TAN media, user's bank accounts and may even current balance and account transactions of last 90 days.
  */
 open class FinTsClient(
-    protected open val jobExecutor: FinTsJobExecutor
+    protected open val jobExecutor: FinTsJobExecutor // TODO: recreate when callback is set to avoid multithreading issues - but use its configured instances like RequestExecutor
 ) {
 
     companion object {
@@ -31,6 +31,10 @@ open class FinTsClient(
     open val messageLogWithoutSensitiveData: List<MessageLogEntry>
         get() = jobExecutor.messageLogWithoutSensitiveData
 
+    open fun setCallback(callback: FinTsClientCallback) {
+        jobExecutor.callback = callback
+    }
+
 
     /**
      * Retrieves information about bank (e.g. supported HBCI versions, FinTS server address,
diff --git a/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsClientForCustomer.kt b/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsClientForCustomer.kt
index ff252059..d235cc23 100644
--- a/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsClientForCustomer.kt
+++ b/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsClientForCustomer.kt
@@ -36,6 +36,10 @@ open class FinTsClientForCustomer(
     open val messageLogWithoutSensitiveData: List<MessageLogEntry>
         get() = client.messageLogWithoutSensitiveData
 
+    open fun setCallback(callback: FinTsClientCallback) {
+        client.setCallback(callback)
+    }
+
 
     open fun addAccountAsync(callback: (AddAccountResponse) -> Unit) {
         addAccountAsync(bank.toAddAccountParameter(), callback)
diff --git a/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsJobExecutor.kt b/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsJobExecutor.kt
index 202b220f..1cd27e7f 100644
--- a/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsJobExecutor.kt
+++ b/fints4k/src/commonMain/kotlin/net/dankito/banking/fints/FinTsJobExecutor.kt
@@ -31,7 +31,7 @@ import net.dankito.utils.multiplatform.ObjectReference
  * In almost all cases you want to use [FinTsClient] which wraps these business transactions to a higher level API.
  */
 open class FinTsJobExecutor(
-    protected open val callback: FinTsClientCallback,
+    open var callback: FinTsClientCallback,
     protected open val requestExecutor: RequestExecutor = RequestExecutor(),
     protected open val messageBuilder: MessageBuilder = MessageBuilder(),
     protected open val mt940Parser: IAccountTransactionsParser = Mt940AccountTransactionsParser(),