diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index f6e8f26922..d771b82736 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -454,6 +454,9 @@ Release 2.5.0 - UNRELEASED
     HDFS-6447. balancer should timestamp the completion message.
     (Juan Yu via wang).
 
+    HDFS-6463. Clarify behavior of AclStorage#createFsPermissionForExtendedAcl
+    in comments. (cnauroth)
+
   OPTIMIZATIONS
 
     HDFS-6214. Webhdfs has poor throughput for files >2GB (daryn)
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclStorage.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclStorage.java
index 841fcb8e43..c15d64e607 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclStorage.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclStorage.java
@@ -338,6 +338,10 @@ private static AclFeature createAclFeature(List<AclEntry> accessEntries,
    * ACL, based on its access ACL entries.  For a correctly sorted ACL, the
    * first entry is the owner and the last 2 entries are the mask and other
    * entries respectively.  Also preserve sticky bit and toggle ACL bit on.
+   * Note that this method intentionally copies the permissions of the mask
+   * entry into the FsPermission group permissions.  This is consistent with the
+   * POSIX ACLs model, which presents the mask as the permissions of the group
+   * class.
    *
    * @param accessEntries List<AclEntry> access ACL entries
    * @param existingPerm FsPermission existing permissions