diff --git a/bootstraptest/test_knownbug.rb b/bootstraptest/test_knownbug.rb
index 0b8c795cde..f978e24f6a 100644
--- a/bootstraptest/test_knownbug.rb
+++ b/bootstraptest/test_knownbug.rb
@@ -12,3 +12,38 @@ assert_finish 1, %q{
   sleep 0.1
   w.write "a"
 }, '[ruby-dev:31866]'
+
+assert_equal "[[nil, 1, 1, nil, nil], [nil, 2, 2, nil]]", %q{
+  def tvar(var, val)
+    old = Thread.current[var]
+    begin
+      Thread.current[var] = val
+      yield
+    ensure
+      Thread.current[var] = old
+    end
+  end
+  ary1 = []
+  ary2 = []
+  fb = Fiber.new {
+    ary2 << Thread.current[:v]
+    tvar(:v, 2) {
+      ary2 << Thread.current[:v]
+      Fiber.yield
+      ary2 << Thread.current[:v]
+    }
+    ary2 << Thread.current[:v]
+    Fiber.yield
+    ary2 << Thread.current[:v]
+  }
+  ary1 << Thread.current[:v]
+  tvar(:v,1) {
+    ary1 << Thread.current[:v]
+    fb.resume
+    ary1 << Thread.current[:v]
+  }
+  ary1 << Thread.current[:v]
+  fb.resume
+  ary1 << Thread.current[:v]
+  [ary1, ary2]
+}