diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java
index 6672cd2375..e72c499624 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java
@@ -416,7 +416,7 @@ public void testAddOneNewVolume()
       minNumBlocks = Math.min(minNumBlocks, blockList.getNumberOfBlocks());
       maxNumBlocks = Math.max(maxNumBlocks, blockList.getNumberOfBlocks());
     }
-    assertTrue(Math.abs(maxNumBlocks - maxNumBlocks) <= 1);
+    assertTrue(Math.abs(maxNumBlocks - minNumBlocks) <= 1);
     verifyFileLength(cluster.getFileSystem(), testFile, numBlocks);
   }