diff --git a/CHANGES.txt b/CHANGES.txt
index 5293580bfc..a849897c2d 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,6 @@
 2.1.0
+Merged from 2.0:
+ * Fix NPE in StreamTransferTask.createMessageForRetry() (CASSANDRA-7323)
 Merged from 1.2:
 * Use LOCAL_ONE for non-superuser auth queries (CASSANDRA-7328)
 
diff --git a/src/java/org/apache/cassandra/streaming/StreamTransferTask.java b/src/java/org/apache/cassandra/streaming/StreamTransferTask.java
index 2f3795620a..2fe75fab91 100644
--- a/src/java/org/apache/cassandra/streaming/StreamTransferTask.java
+++ b/src/java/org/apache/cassandra/streaming/StreamTransferTask.java
@@ -99,11 +99,12 @@ public class StreamTransferTask extends StreamTask
         return new ArrayList<>(files.values());
     }
 
-    public OutgoingFileMessage createMessageForRetry(int sequenceNumber)
+    public synchronized OutgoingFileMessage createMessageForRetry(int sequenceNumber)
     {
         // remove previous time out task to be rescheduled later
         ScheduledFuture future = timeoutTasks.get(sequenceNumber);
-        future.cancel(false);
+        if (future != null)
+            future.cancel(false);
         return files.get(sequenceNumber);
     }