diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/AbstractMapWritable.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/AbstractMapWritable.java
index cc1e517eaa586..9e0674b942514 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/AbstractMapWritable.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/AbstractMapWritable.java
@@ -195,23 +195,23 @@ public void write(DataOutput out) throws IOException {
   
   @Override
   public void readFields(DataInput in) throws IOException {
-    
+
     // Get the number of "unknown" classes
-    
     newClasses = in.readByte();
-    
+
+    // Get the class loader of the current thread because
+    // Class.forName does not have the job jar in its path
+    ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
+
     // Then read in the class names and add them to our tables
-    
     for (int i = 0; i < newClasses; i++) {
       byte id = in.readByte();
       String className = in.readUTF();
       try {
-        addToMap(Class.forName(className), id);
-        
+        addToMap(classLoader.loadClass(className), id);
       } catch (ClassNotFoundException e) {
-        throw new IOException("can't find class: " + className + " because "+
-            e.getMessage());
+        throw new IOException(e);
       }
     }
-  }    
+  }
 }