diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/InvalidateBlocks.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/InvalidateBlocks.java
index b72c78ff24d..f1a201d7f66 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/InvalidateBlocks.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/InvalidateBlocks.java
@@ -32,6 +32,7 @@ import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
 import org.apache.hadoop.hdfs.util.LightWeightHashSet;
+import org.apache.hadoop.util.StringUtils;
 import org.apache.hadoop.util.Time;
 import org.apache.hadoop.hdfs.DFSUtil;
 
@@ -151,7 +152,7 @@ class InvalidateBlocks {
       final LightWeightHashSet<Block> blocks = entry.getValue();
       if (blocks.size() > 0) {
         out.println(entry.getKey());
-        out.println(blocks);
+        out.println(StringUtils.join(',', blocks));
       }
     }
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestMetaSave.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestMetaSave.java
index 6a82cc356d7..14f9382e906 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestMetaSave.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestMetaSave.java
@@ -172,6 +172,7 @@ public class TestMetaSave {
       //skip 2 lines to reach HDFS-9033 scenario.
       line = reader.readLine();
       line = reader.readLine();
+      assertTrue(line.contains("blk"));
       // skip 1 line for Corrupt Blocks section.
       line = reader.readLine();
       line = reader.readLine();