diff --git a/test/ruby/test_flip.rb b/test/ruby/test_flip.rb
index bd14228a8c..fc62d93ae6 100644
--- a/test/ruby/test_flip.rb
+++ b/test/ruby/test_flip.rb
@@ -18,4 +18,25 @@ class TestFlip < Test::Unit::TestCase
     v = eval("vs.select {|n| if n==3..n==6 then 1 end}")
     assert_equal([*3..6], v, bug7671)
   end
+
+  def test_shared_thread
+    ff = proc {|n| true if n==3..n==5}
+    v = 1..9
+    a = true
+    th = Thread.new {
+      v.select {|i|
+        Thread.pass while a
+        ff[i].tap {a = true}
+      }
+    }
+    v1 = v.select {|i|
+      Thread.pass until a
+      ff[i].tap {a = false}
+    }
+    v2 = th.value
+    expected = [3, 4, 5]
+    mesg = 'flip-flop should be separated per threads'
+    assert_equal(expected, v1, mesg)
+    assert_equal(expected, v2, mesg)
+  end
 end