diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 8e10c75c5f6..9a671af032f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -450,6 +450,8 @@ Branch-2 ( Unreleased changes )
     HDFS-3548. NamenodeFsck.copyBlock fails to create a Block Reader.
     (Colin Patrick McCabe via eli)
 
+    HDFS-3615. Two BlockTokenSecretManager findbugs warnings. (atm)
+
   BREAKDOWN OF HDFS-3042 SUBTASKS
 
     HDFS-2185. HDFS portion of ZK-based FailoverController (todd)
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/security/token/block/BlockTokenSecretManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/security/token/block/BlockTokenSecretManager.java
index 832b0e75141..35e4c687c7d 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/security/token/block/BlockTokenSecretManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/security/token/block/BlockTokenSecretManager.java
@@ -116,7 +116,7 @@ public class BlockTokenSecretManager extends
   }
   
   @VisibleForTesting
-  public void setSerialNo(int serialNo) {
+  public synchronized void setSerialNo(int serialNo) {
     this.serialNo = (serialNo & LOW_MASK) | (nnIndex << 31);
   }
 
@@ -189,7 +189,7 @@ public class BlockTokenSecretManager extends
    * Update block keys if update time > update interval.
    * @return true if the keys are updated.
    */
-  public boolean updateKeys(final long updateTime) throws IOException {
+  public synchronized boolean updateKeys(final long updateTime) throws IOException {
     if (updateTime > keyUpdateInterval) {
       return updateKeys();
     }
@@ -371,7 +371,7 @@ public class BlockTokenSecretManager extends
   }
   
   @VisibleForTesting
-  public void setKeyUpdateIntervalForTesting(long millis) {
+  public synchronized void setKeyUpdateIntervalForTesting(long millis) {
     this.keyUpdateInterval = millis;
   }
 
@@ -381,7 +381,7 @@ public class BlockTokenSecretManager extends
   }
   
   @VisibleForTesting
-  public int getSerialNoForTesting() {
+  public synchronized int getSerialNoForTesting() {
     return serialNo;
   }