diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DiskBalancer.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DiskBalancer.java
index 75e5d9ad3d..f8d4ea40d4 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DiskBalancer.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DiskBalancer.java
@@ -905,6 +905,11 @@ private ExtendedBlock getBlockToCopy(FsVolumeSpi.BlockIterator iter,
       while (!iter.atEnd() && item.getErrorCount() < getMaxError(item)) {
         try {
           ExtendedBlock block = iter.nextBlock();
+          if(null == block){
+            LOG.info("NextBlock call returned null.No valid block to copy. {}",
+                    item.toJson());
+            return block;
+          }
 
           if (block != null) {
             // A valid block is a finalized block, we iterate until we get