diff --git a/ChangeLog b/ChangeLog
index 6c5053eabc..738ec2dfa7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sun Sep 22 19:00:28 2013  Benoit Daloze  <eregontp@gmail.com>
+
+	* benchmark/bm_app_answer.rb: revert r42990, benchmark scripts should
+	  be self-contained and avoid dependencies, especially such small one.
+	  See https://github.com/ruby/ruby/pull/393#issuecomment-24861301.
+
 Sat Sep 21 20:11:06 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* process.c (rb_fork_internal): remove cloexec setting on pipes
diff --git a/benchmark/bm_app_answer.rb b/benchmark/bm_app_answer.rb
index 2aea289def..3cd8a8fd37 100644
--- a/benchmark/bm_app_answer.rb
+++ b/benchmark/bm_app_answer.rb
@@ -1,4 +1,12 @@
-require_relative 'other-lang/ack'
+def ack(m, n)
+  if m == 0 then
+    n + 1
+  elsif n == 0 then
+    ack(m - 1, 1)
+  else
+    ack(m - 1, ack(m, n - 1))
+  end
+end
 
 def the_answer_to_life_the_universe_and_everything
   (ack(3,7).to_s.split(//).inject(0){|s,x| s+x.to_i}.to_s + "2" ).to_i