diff --git a/ChangeLog b/ChangeLog
index 8b9c27959e..9e7d91d0e4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Sep 20 02:18:10 2015  Tanaka Akira  <akr@fsij.org>
+
+	* test/lib/envutil.rb: mkfifo command based File.mkfifo method
+	  definition removed.
+
 Fri Sep 18 20:11:11 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* file.c (rb_file_s_mkfifo): implement File.mkfifo.
diff --git a/test/lib/envutil.rb b/test/lib/envutil.rb
index b37d180c20..1e0cf61b95 100644
--- a/test/lib/envutil.rb
+++ b/test/lib/envutil.rb
@@ -3,11 +3,6 @@ require "open3"
 require "timeout"
 require_relative "find_executable"
 
-def File.mkfifo(fn)
-  ret = system("mkfifo", fn)
-  raise NotImplementedError, "mkfifo fails" if !ret
-end unless File.respond_to?(:mkfifo) or /mswin|mingw|bccwin/ =~ RUBY_PLATFORM
-
 module EnvUtil
   def rubybin
     if ruby = ENV["RUBY"]