diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index c989514a0ae..41465e3f57a 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -33,6 +33,9 @@ Release 2.7.3 - UNRELEASED
     HADOOP-12565. Replace DSA with RSA for SSH key type in SingleCluster.md.
     (Mingliang Liu via aajisaka)
 
+    HADOOP-12602. TestMetricsSystemImpl#testQSize occasionally fails.
+    (Masatake Iwasaki via aajisaka)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/impl/TestMetricsSystemImpl.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/impl/TestMetricsSystemImpl.java
index ecf2cc85572..0463f48c5d5 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/impl/TestMetricsSystemImpl.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/metrics2/impl/TestMetricsSystemImpl.java
@@ -441,6 +441,7 @@ public class TestMetricsSystemImpl {
   @Test
   public void testQSize() throws Exception {
     new ConfigBuilder().add("*.period", 8)
+        .add("*.queue.capacity", 2)
         .add("test.sink.test.class", TestSink.class.getName())
         .save(TestMetricsConfig.getTestFilename("hadoop-metrics2-test"));
     MetricsSystemImpl ms = new MetricsSystemImpl("Test");