diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index 8ad53ac78e..94441db244 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -636,11 +636,14 @@ class TestProcess < Test::Unit::TestCase
         class E < StandardError; end
         trap(:USR1) { raise E }
         begin
+          puts "start"
+          STDOUT.flush
           system("cat", :in => "fifo")
         rescue E
           puts "ok"
         end
       EOS
+        assert_equal("start\n", io.gets)
         sleep 0.5
         Process.kill(:USR1, io.pid)
         assert_equal("ok\n", io.read)