diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6fcab528a3..e87ba93661 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,48 @@
 
 librdkafka v2.3.1 is a feature release:
 
+* Fix segfault when using long client id because of erased segment when using flexver. (#4689)
+* Fix for an idempotent producer error, with a message batch not reconstructed
+  identically when retried (#4750)
+
+
+## Enhancements
+
+  * Update bundled lz4 (used when `./configure --disable-lz4-ext`) to
+    [v1.9.4](/~https://github.com/lz4/lz4/releases/tag/v1.9.4), which contains
+    bugfixes and performance improvements (#4726).
+
+
+## Fixes
+
+### General fixes
+
+*  Issues: [confluentinc/confluent-kafka-dotnet#2084](/~https://github.com/confluentinc/confluent-kafka-dotnet/issues/2084)
+   Fix segfault when a segment is erased and more data is written to the buffer.
+   Happens since 1.x when a portion of the buffer (segment) is erased for flexver or compression.
+   More likely to happen since 2.1.0, because of the upgrades to flexver, with certain string sizes like a long client id (#4689).
+
+### Idempotent producer fixes
+
+ * Issues: #4736
+   Fix for an idempotent producer error, with a message batch not reconstructed
+   identically when retried. Caused the error message "Local: Inconsistent state: Unable to reconstruct MessageSet".
+   Happening on large batches. Solved by using the same backoff baseline for all messages
+   in the batch.
+   Happens since 2.2.0 (#4750).
+
+
+
+# librdkafka v2.4.0
+
+librdkafka v2.4.0 is a feature release:
+
+ * [KIP-848](https://cwiki.apache.org/confluence/display/KAFKA/KIP-848%3A+The+Next+Generation+of+the+Consumer+Rebalance+Protocol): The Next Generation of the Consumer Rebalance Protocol.
+   **Early Access**: This should be used only for evaluation and must not be used in production. Features and contract of this KIP might change in future (#4610).
+ * [KIP-467](https://cwiki.apache.org/confluence/display/KAFKA/KIP-467%3A+Augment+ProduceResponse+error+messaging+for+specific+culprit+records): Augment ProduceResponse error messaging for specific culprit records (#4583).
+ * [KIP-516](https://cwiki.apache.org/confluence/display/KAFKA/KIP-516%3A+Topic+Identifiers)
+   Continue partial implementation by adding a metadata cache by topic id
+   and updating the topic id corresponding to the partition name (#4676)
  * Upgrade OpenSSL to v3.0.12 (while building from source) with various security fixes,
    check the [release notes](https://www.openssl.org/news/cl30.txt).
 
diff --git a/src/rdkafka_partition.c b/src/rdkafka_partition.c
index 357c137db8..9ea776abe9 100644
--- a/src/rdkafka_partition.c
+++ b/src/rdkafka_partition.c
@@ -896,6 +896,7 @@ int rd_kafka_retry_msgq(rd_kafka_msgq_t *destq,
                         int retry_max_ms) {
         rd_kafka_msgq_t retryable = RD_KAFKA_MSGQ_INITIALIZER(retryable);
         rd_kafka_msg_t *rkm, *tmp;
+        rd_ts_t now;
         int64_t jitter = rd_jitter(100 - RD_KAFKA_RETRY_JITTER_PERCENT,
                                    100 + RD_KAFKA_RETRY_JITTER_PERCENT);
         /* Scan through messages to see which ones are eligible for retry,
@@ -903,7 +904,14 @@ int rd_kafka_retry_msgq(rd_kafka_msgq_t *destq,
          * set backoff time for first message and optionally
          * increase retry count for each message.
          * Sorted insert is not necessary since the original order
-         * srcq order is maintained. */
+         * srcq order is maintained.
+         *
+         * Start timestamp for calculating backoff is common,
+         * to avoid that messages from the same batch
+         * have different backoff, as they need to be retried
+         * by reconstructing the same batch, when idempotency is
+         * enabled. */
+        now = rd_clock();
         TAILQ_FOREACH_SAFE(rkm, &srcq->rkmq_msgs, rkm_link, tmp) {
                 if (rkm->rkm_u.producer.retries + incr_retry > max_retries)
                         continue;
@@ -927,7 +935,7 @@ int rd_kafka_retry_msgq(rd_kafka_msgq_t *destq,
                         backoff = jitter * backoff * 10;
                         if (backoff > retry_max_ms * 1000)
                                 backoff = retry_max_ms * 1000;
-                        backoff = rd_clock() + backoff;
+                        backoff = now + backoff;
                 }
                 rkm->rkm_u.producer.ts_backoff = backoff;