Index: src/java/org/apache/nutch/crawl/GeneratorJob.java
===================================================================
--- src/java/org/apache/nutch/crawl/GeneratorJob.java	(revision 1680939)
+++ src/java/org/apache/nutch/crawl/GeneratorJob.java	(working copy)
@@ -170,7 +170,11 @@
     }
 
     // map to inverted subset due for fetch, sort by score
-    Long topN = (Long) args.get(Nutch.ARG_TOPN);
+    try {
+      Long topN = (Long) args.get(Nutch.ARG_TOPN);
+    } catch(Exception e) {
+      topN = Long.parseLong(args.get(Nutch.ARG_TOPN).toString());
+    }
     Long curTime = (Long) args.get(Nutch.ARG_CURTIME);
     if (curTime == null) {
       curTime = System.currentTimeMillis();