diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-1623.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-1623.txt
index 6c932936712..d5f4d0d7f79 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-1623.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-1623.txt
@@ -39,3 +39,5 @@ HDFS-2622. Fix TestDFSUpgrade in HA branch. (todd)
 HDFS-2612. Handle refreshNameNodes in federated HA clusters (todd)
 
 HDFS-2623. Add test case for hot standby capability (todd)
+
+HDFS-2626. BPOfferService.verifyAndSetNamespaceInfo needs to be synchronized (todd)
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
index 62b825be56f..eb611bffcb0 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
@@ -262,7 +262,7 @@ DataNode getDataNode() {
    * verifies that this namespace matches (eg to prevent a misconfiguration
    * where a StandbyNode from a different cluster is specified)
    */
-  void verifyAndSetNamespaceInfo(NamespaceInfo nsInfo) throws IOException {
+  synchronized void verifyAndSetNamespaceInfo(NamespaceInfo nsInfo) throws IOException {
     if (this.bpNSInfo == null) {
       this.bpNSInfo = nsInfo;
       
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
index e83ec99c1ac..bf49cc0a6b9 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java
@@ -336,8 +336,6 @@ DatanodeCommand blockReport() throws IOException {
   
   HeartbeatResponse sendHeartBeat() throws IOException {
     LOG.info("heartbeat: " + this);
-    // TODO: saw an NPE here - maybe if the two BPOS register at
-    // same time, this one won't block on the other one?
     return bpNamenode.sendHeartbeat(bpRegistration,
         dn.getFSDataset().getCapacity(),
         dn.getFSDataset().getDfsUsed(),
@@ -632,4 +630,4 @@ void reRegister() throws IOException {
     }
   }
 
-}
\ No newline at end of file
+}