Index: src/java/org/apache/nutch/crawl/LinkDbMerger.java
===================================================================
--- src/java/org/apache/nutch/crawl/LinkDbMerger.java	(revision 559283)
+++ src/java/org/apache/nutch/crawl/LinkDbMerger.java	(working copy)
@@ -120,6 +120,7 @@
     job.setMapperClass(LinkDbFilter.class);
     job.setBoolean(LinkDbFilter.URL_NORMALIZING, normalize);
     job.setBoolean(LinkDbFilter.URL_FILTERING, filter);
+    job.setCombinerClass(LinkDbMerger.class);
     job.setReducerClass(LinkDbMerger.class);
 
     job.setOutputPath(newLinkDb);