Index: main/core/src/main/java/hudson/tasks/Ant.java
===================================================================
--- main/core/src/main/java/hudson/tasks/Ant.java	(revision 24675)
+++ main/core/src/main/java/hudson/tasks/Ant.java	(working copy)
@@ -171,7 +171,7 @@
         }
 
         if(buildFile!=null) {
-            args.add("-file", buildFilePath.getName());
+            args.add("-file", buildFilePath.getRemote());
         }
 
         args.addKeyValuePairs("-D",build.getBuildVariables());
@@ -204,7 +204,7 @@
 
         long startTime = System.currentTimeMillis();
         try {
-            int r = launcher.launch().cmds(args).envs(env).stdout(listener).pwd(buildFilePath.getParent()).join();
+            int r = launcher.launch().cmds(args).envs(env).stdout(listener).pwd(build.getWorkspace()).join();
             return r==0;
         } catch (IOException e) {
             Util.displayIOException(e,listener);