diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 985584f9a96..1537876e945 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -68,6 +68,9 @@ Release 2.0.5-beta - UNRELEASED
     HDFS-4592. Default values for access time precision are out of sync between
     hdfs-default.xml and the code. (atm)
 
+    HDFS-4522. LightWeightGSet expects incrementing a volatile to be atomic.
+    (Colin Patrick McCabe via atm)
+
 Release 2.0.4-alpha - UNRELEASED
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/LightWeightGSet.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/LightWeightGSet.java
index 32d80c25516..cb0412d0344 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/LightWeightGSet.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/LightWeightGSet.java
@@ -72,7 +72,7 @@ public class LightWeightGSet<K, E extends K> implements GSet<K, E> {
   /** Modification version for fail-fast.
    * @see ConcurrentModificationException
    */
-  private volatile int modification = 0;
+  private int modification = 0;
 
   /**
    * @param recommended_length Recommended size of the internal array.