diff --git a/core/src/main/scala/kafka/coordinator/transaction/TransactionLog.scala b/core/src/main/scala/kafka/coordinator/transaction/TransactionLog.scala
index 17e640ebb33..829e9e6bf65 100644
--- a/core/src/main/scala/kafka/coordinator/transaction/TransactionLog.scala
+++ b/core/src/main/scala/kafka/coordinator/transaction/TransactionLog.scala
@@ -281,7 +281,7 @@ object TransactionLog {
       case Some(txnMetadata) => s"producerId:${txnMetadata.producerId}," +
         s"producerEpoch:${txnMetadata.producerEpoch}," +
         s"state=${txnMetadata.state}," +
-        s"partitions=${txnMetadata.topicPartitions}," +
+        s"partitions=${txnMetadata.topicPartitions.mkString("[", ",", "]")}," +
         s"txnLastUpdateTimestamp=${txnMetadata.txnLastUpdateTimestamp}," +
         s"txnTimeoutMs=${txnMetadata.txnTimeoutMs}"
     }
diff --git a/core/src/test/scala/unit/kafka/coordinator/transaction/TransactionLogTest.scala b/core/src/test/scala/unit/kafka/coordinator/transaction/TransactionLogTest.scala
index e9bf6d51454..e9bdf3110a8 100644
--- a/core/src/test/scala/unit/kafka/coordinator/transaction/TransactionLogTest.scala
+++ b/core/src/test/scala/unit/kafka/coordinator/transaction/TransactionLogTest.scala
@@ -123,7 +123,7 @@ class TransactionLogTest {
     val (keyStringOpt, valueStringOpt) = TransactionLog.formatRecordKeyAndValue(transactionMetadataRecord)
     assertEquals(Some(s"transaction_metadata::transactionalId=$transactionalId"), keyStringOpt)
     assertEquals(Some(s"producerId:$producerId,producerEpoch:$producerEpoch,state=Ongoing," +
-      s"partitions=Set($topicPartition),txnLastUpdateTimestamp=0,txnTimeoutMs=$transactionTimeoutMs"), valueStringOpt)
+      s"partitions=[$topicPartition],txnLastUpdateTimestamp=0,txnTimeoutMs=$transactionTimeoutMs"), valueStringOpt)
   }
 
   @Test