diff --git a/ChangeLog b/ChangeLog
index 7f72c3004c..239d380afe 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Nov  6 10:03:00 2016  Shugo Maeda  <shugo@ruby-lang.org>
+
+	* test/ruby/test_optimization.rb (test_tailcall_interrupted_by_sigint):
+	  don't use sleep to run faster.
+
 Sun Nov  6 09:58:47 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* process.c (rb_exec_fillarg): honor the given path environment
diff --git a/test/ruby/test_optimization.rb b/test/ruby/test_optimization.rb
index c035a112cb..2589494596 100644
--- a/test/ruby/test_optimization.rb
+++ b/test/ruby/test_optimization.rb
@@ -328,18 +328,21 @@ eval <<EOF
 def foo
   foo
 end
+puts("start")
+STDOUT.flush
 foo
 EOF
 EOS
-    err = EnvUtil.invoke_ruby([], "", true, true, {}) {
+    status, err = EnvUtil.invoke_ruby([], "", true, true, {}) {
       |in_p, out_p, err_p, pid|
       in_p.write(script)
       in_p.close
-      sleep(1)
+      out_p.gets
       Process.kill(:SIGINT, pid)
-      Process.wait(pid)
-      err_p.read
+      *, stat = Process.wait2(pid)
+      [stat, err_p.read]
     }
+    assert_equal(Signal.list["INT"], status.termsig)
     assert_match(/Interrupt/, err, bug)
   end