diff --git a/hadoop-mapreduce-project/CHANGES.txt b/hadoop-mapreduce-project/CHANGES.txt
index a44f2e41ada..7dc4436a887 100644
--- a/hadoop-mapreduce-project/CHANGES.txt
+++ b/hadoop-mapreduce-project/CHANGES.txt
@@ -92,6 +92,9 @@ Trunk (Unreleased)
     MAPREDUCE-4791. Javadoc for KeyValueTextInputFormat should include default 
       separator and how to change it (Akira AJISAKA via aw)
 
+    MAPREDUCE-5906. Inconsistent configuration in property 
+      "mapreduce.reduce.shuffle.input.buffer.percent" (Akira AJISAKA via aw)
+
   BUG FIXES
 
     MAPREDUCE-5714. Removed forceful JVM exit in shutDownJob.  
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/MRJobConfig.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/MRJobConfig.java
index 4795af78d2a..0a586967d01 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/MRJobConfig.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/MRJobConfig.java
@@ -265,6 +265,7 @@ public interface MRJobConfig {
   public static final String REDUCE_MEMORY_TOTAL_BYTES = "mapreduce.reduce.memory.totalbytes";
 
   public static final String SHUFFLE_INPUT_BUFFER_PERCENT = "mapreduce.reduce.shuffle.input.buffer.percent";
+  public static final float DEFAULT_SHUFFLE_INPUT_BUFFER_PERCENT = 0.70f;
 
   public static final String SHUFFLE_MEMORY_LIMIT_PERCENT
     = "mapreduce.reduce.shuffle.memory.limit.percent";
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/task/reduce/MergeManagerImpl.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/task/reduce/MergeManagerImpl.java
index 4d83995dcfd..49aa8576d60 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/task/reduce/MergeManagerImpl.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/task/reduce/MergeManagerImpl.java
@@ -156,7 +156,8 @@ public class MergeManagerImpl<K, V> implements MergeManager<K, V> {
     this.rfs = ((LocalFileSystem)localFS).getRaw();
     
     final float maxInMemCopyUse =
-      jobConf.getFloat(MRJobConfig.SHUFFLE_INPUT_BUFFER_PERCENT, 0.90f);
+      jobConf.getFloat(MRJobConfig.SHUFFLE_INPUT_BUFFER_PERCENT,
+          MRJobConfig.DEFAULT_SHUFFLE_INPUT_BUFFER_PERCENT);
     if (maxInMemCopyUse > 1.0 || maxInMemCopyUse < 0.0) {
       throw new IllegalArgumentException("Invalid value for " +
           MRJobConfig.SHUFFLE_INPUT_BUFFER_PERCENT + ": " +