diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index 84100e18c4..84898cd29b 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -120,6 +120,9 @@ Trunk (Unreleased)
 
     HDFS-4904. Remove JournalService. (Arpit Agarwal via cnauroth)
 
+    HDFS-5144. Document time unit to NameNodeMetrics. (Akira Ajisaka via
+    suresh)
+
   OPTIMIZATIONS
 
   BUG FIXES
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/metrics/NameNodeMetrics.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/metrics/NameNodeMetrics.java
index d02186d34b..9aac83ddaf 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/metrics/NameNodeMetrics.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/metrics/NameNodeMetrics.java
@@ -80,8 +80,10 @@ public class NameNodeMetrics {
   @Metric("Block report") MutableRate blockReport;
   MutableQuantiles[] blockReportQuantiles;
 
-  @Metric("Duration in SafeMode at startup") MutableGaugeInt safeModeTime;
-  @Metric("Time loading FS Image at startup") MutableGaugeInt fsImageLoadTime;
+  @Metric("Duration in SafeMode at startup in msec")
+  MutableGaugeInt safeModeTime;
+  @Metric("Time loading FS Image at startup in msec")
+  MutableGaugeInt fsImageLoadTime;
 
   NameNodeMetrics(String processName, String sessionId, int[] intervals) {
     registry.tag(ProcessName, processName).tag(SessionId, sessionId);