diff --git a/CHANGES.txt b/CHANGES.txt
index 950ed48917..cae6a43c50 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -3,6 +3,7 @@
  * Allow nodetool garbagecollect to take a user defined list of SSTables (CASSANDRA-16767)
  * Add a guardrail for misprepared statements (CASSANDRA-21139)
 Merged from 6.0:
+ * Fix ReadCommand serializedSize() using incorrect epoch (CASSANDRA-21438)
  * Allocation improvements in ProtocolVersion, StorageProxy and MerkleTree (CASSANDRA-21199)
  * Don’t leave autocompaction disabled during bootstrap and replace (CASSANDRA-21236)
  * Make nodetool abortbootstrap more robust (CASSANDRA-21235)
diff --git a/src/java/org/apache/cassandra/db/ReadCommand.java b/src/java/org/apache/cassandra/db/ReadCommand.java
index e1c0a21834..53ad6b3d1b 100644
--- a/src/java/org/apache/cassandra/db/ReadCommand.java
+++ b/src/java/org/apache/cassandra/db/ReadCommand.java
@@ -1520,7 +1520,7 @@ public abstract class ReadCommand extends AbstractReadQuery
             return 2 // kind + flags
                    + (command.isDigestQuery() ? TypeSizes.sizeofUnsignedVInt(command.digestVersion()) : 0)
                    + command.metadata().id.serializedSize()
-                   + (version >= MessagingService.VERSION_60 ? Epoch.serializer.serializedSize(command.metadata().epoch) : 0)
+                   + (version >= MessagingService.VERSION_60 ? Epoch.serializer.serializedSize(command.serializedAtEpoch) : 0)
                    + TypeSizes.INT_SIZE // command.nowInSec() is serialized as uint
                    + ColumnFilter.serializer.serializedSize(command.columnFilter(), version)
                    + RowFilter.serializer.serializedSize(command.rowFilter(), version)