diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index d9ae1cd9327..371fb50033a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -131,6 +131,9 @@ Release 2.3.0 - UNRELEASED
     HDFS-5336. DataNode should not output 'StartupProgress' metrics.
     (Akira Ajisaka via cnauroth)
 
+    HDFS-5400.  DFS_CLIENT_MMAP_CACHE_THREAD_RUNS_PER_TIMEOUT constant is set
+    to the wrong value.  (Colin Patrick McCabe)
+
 Release 2.2.1 - UNRELEASED
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
index de75ac15801..e195a071f81 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
@@ -383,7 +383,7 @@ public class DFSConfigKeys extends CommonConfigurationKeys {
   public static final int DFS_CLIENT_MMAP_CACHE_SIZE_DEFAULT = 1024;
   public static final String DFS_CLIENT_MMAP_CACHE_TIMEOUT_MS = "dfs.client.mmap.cache.timeout.ms";
   public static final long DFS_CLIENT_MMAP_CACHE_TIMEOUT_MS_DEFAULT  = 15 * 60 * 1000;
-  public static final String DFS_CLIENT_MMAP_CACHE_THREAD_RUNS_PER_TIMEOUT = "dfs.client.mmap.cache.timeout.ms";
+  public static final String DFS_CLIENT_MMAP_CACHE_THREAD_RUNS_PER_TIMEOUT = "dfs.client.mmap.cache.thread.runs.per.timeout";
   public static final int DFS_CLIENT_MMAP_CACHE_THREAD_RUNS_PER_TIMEOUT_DEFAULT  = 4;
 
   // property for fsimage compression