diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/MapTask.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/MapTask.java
index 45431e65ed8..3753fba1f5f 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/MapTask.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/MapTask.java
@@ -967,7 +967,8 @@ public class MapTask extends Task {
       //sanity checks
       final float spillper =
         job.getFloat(JobContext.MAP_SORT_SPILL_PERCENT, (float)0.8);
-      final int sortmb = job.getInt(JobContext.IO_SORT_MB, 100);
+      final int sortmb = job.getInt(MRJobConfig.IO_SORT_MB,
+          MRJobConfig.DEFAULT_IO_SORT_MB);
       indexCacheMemoryLimit = job.getInt(JobContext.INDEX_CACHE_MEMORY_LIMIT,
                                          INDEX_CACHE_MEMORY_LIMIT_DEFAULT);
       if (spillper > (float)1.0 || spillper <= (float)0.0) {
@@ -1920,7 +1921,8 @@ public class MapTask extends Task {
             }
           }
 
-          int mergeFactor = job.getInt(JobContext.IO_SORT_FACTOR, 100);
+          int mergeFactor = job.getInt(MRJobConfig.IO_SORT_FACTOR,
+              MRJobConfig.DEFAULT_IO_SORT_FACTOR);
           // sort the segments only if there are intermediate merges
           boolean sortSegments = segmentList.size() > mergeFactor;
           //merge
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 1325b743a10..2ad86ef892f 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
@@ -215,8 +215,12 @@ public interface MRJobConfig {
 
   public static final String IO_SORT_FACTOR = "mapreduce.task.io.sort.factor";
 
+  public static final int DEFAULT_IO_SORT_FACTOR = 10;
+
   public static final String IO_SORT_MB = "mapreduce.task.io.sort.mb";
 
+  public static final int DEFAULT_IO_SORT_MB = 100;
+
   public static final String INDEX_CACHE_MEMORY_LIMIT = "mapreduce.task.index.cache.limit.bytes";
 
   public static final String PRESERVE_FAILED_TASK_FILES = "mapreduce.task.files.preserve.failedtasks";
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 09fe0cbbfc9..f26c10ac592 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
@@ -175,7 +175,8 @@ public class MergeManagerImpl<K, V> implements MergeManager<K, V> {
         MRJobConfig.REDUCE_MEMORY_TOTAL_BYTES,
         Runtime.getRuntime().maxMemory()) * maxInMemCopyUse);
 
-    this.ioSortFactor = jobConf.getInt(MRJobConfig.IO_SORT_FACTOR, 100);
+    this.ioSortFactor = jobConf.getInt(MRJobConfig.IO_SORT_FACTOR,
+        MRJobConfig.DEFAULT_IO_SORT_FACTOR);
 
     final float singleShuffleMemoryLimitPercent =
         jobConf.getFloat(MRJobConfig.SHUFFLE_MEMORY_LIMIT_PERCENT,
diff --git a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/task/reduce/TestMergeManager.java b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/task/reduce/TestMergeManager.java
index 325d2f9a5c7..1e0dddd1986 100644
--- a/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/task/reduce/TestMergeManager.java
+++ b/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/test/java/org/apache/hadoop/mapreduce/task/reduce/TestMergeManager.java
@@ -207,6 +207,13 @@ public class TestMergeManager {
     }
   }
 
+  @Test
+  public void testIoSortDefaults() {
+    final JobConf jobConf = new JobConf();
+    assertEquals(10, jobConf.getInt(MRJobConfig.IO_SORT_FACTOR, 100));
+    assertEquals(100, jobConf.getInt(MRJobConfig.IO_SORT_MB, 10));
+  }
+
   @SuppressWarnings({ "unchecked", "deprecation" })
   @Test(timeout=10000)
   public void testOnDiskMerger() throws IOException, URISyntaxException,