diff --git a/hadoop-common-project/hadoop-common/CHANGES.txt b/hadoop-common-project/hadoop-common/CHANGES.txt
index bcd48c4c55..0dbe5bc6f7 100644
--- a/hadoop-common-project/hadoop-common/CHANGES.txt
+++ b/hadoop-common-project/hadoop-common/CHANGES.txt
@@ -75,6 +75,8 @@ Trunk (unreleased changes)
     HADOOP-7886. Add toString to FileStatus. (SreeHari via jghoman)
 
   BUGS
+    HADOOP-7851. Configuration.getClasses() never returns the default value. 
+                 (amarrk)
 
     HADOOP-7606. Upgrade Jackson to version 1.7.1 to match the version required
     by Jersey (Alejandro Abdelnur via atm)
diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java
index a3d4de0cb3..164128e14b 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java
@@ -1145,9 +1145,11 @@ public Class<?> getClassByName(String name) throws ClassNotFoundException {
    *         or <code>defaultValue</code>. 
    */
   public Class<?>[] getClasses(String name, Class<?> ... defaultValue) {
-    String[] classnames = getTrimmedStrings(name);
-    if (classnames == null)
+    String valueString = getRaw(name);
+    if (null == valueString) {
       return defaultValue;
+    }
+    String[] classnames = getTrimmedStrings(name);
     try {
       Class<?>[] classes = new Class<?>[classnames.length];
       for(int i = 0; i < classnames.length; i++) {
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestConfiguration.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestConfiguration.java
index f9f14fb848..68f19756a3 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestConfiguration.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/conf/TestConfiguration.java
@@ -837,6 +837,27 @@ public void testGetValByRegex() {
     assertTrue("Picked out wrong key " + key4, !res.containsKey(key4));
   }
 
+  public void testGetClassesShouldReturnDefaultValue() throws Exception {
+    Configuration config = new Configuration();
+    Class<?>[] classes = 
+      config.getClasses("testClassName", Configuration.class);
+    assertEquals(
+        "Not returning expected number of classes. Number of returned classes ="
+            + classes.length, 1, classes.length);
+    assertEquals("Not returning the default class Name", Configuration.class,
+        classes[0]);
+  }
+
+  public void testGetClassesShouldReturnEmptyArray()
+      throws Exception {
+    Configuration config = new Configuration();
+    config.set("testClassName", "");
+    Class<?>[] classes = config.getClasses("testClassName", Configuration.class);
+    assertEquals(
+        "Not returning expected number of classes. Number of returned classes ="
+            + classes.length, 0, classes.length);
+  }
+  
   public static void main(String[] argv) throws Exception {
     junit.textui.TestRunner.main(new String[]{
       TestConfiguration.class.getName()