diff -r d9d8d2e0f701 -r 41c03b7592ed mercurial/filemerge.py
--- a/mercurial/filemerge.py	Sat Nov 08 12:57:42 2014 +0900
+++ b/mercurial/filemerge.py	Sat Nov 08 13:06:22 2014 +0900
@@ -301,8 +301,7 @@
         replace = {'local': a, 'base': b, 'other': c, 'output': out}
         args = util.interpolate(r'\$', replace, args,
                                 lambda s: util.shellquote(util.localpath(s)))
-        r = util.system(toolpath + ' ' + args, cwd=repo.root, environ=env,
-                        out=ui.fout)
+        r = ui.system(toolpath + ' ' + args, cwd=repo.root, environ=env)
         return True, r
     return False, 0