1 files changed, 9 insertions, 1 deletions
diff --git a/test/stringio/test_stringio.rb b/test/stringio/test_stringio.rb
index b0eff57c77..2af6923574 100644
--- a/test/stringio/test_stringio.rb
+++ b/test/stringio/test_stringio.rb
@@ -22,10 +22,11 @@ class TestStringIO < Test::Unit::TestCase
     assert_kind_of StringIO, StringIO.new
     assert_kind_of StringIO, StringIO.new('str')
     assert_kind_of StringIO, StringIO.new('str', 'r+')
+    assert_kind_of StringIO, StringIO.new(nil)
     assert_raise(ArgumentError) { StringIO.new('', 'x') }
     assert_raise(ArgumentError) { StringIO.new('', 'rx') }
     assert_raise(ArgumentError) { StringIO.new('', 'rbt') }
-    assert_raise(TypeError) { StringIO.new(nil) }
+    assert_raise(TypeError) { StringIO.new(Object) }
 
     o = Object.new
     def o.to_str
@@ -40,6 +41,13 @@ class TestStringIO < Test::Unit::TestCase
     assert_kind_of StringIO, StringIO.new(o)
   end
 
+  def test_null
+    io = StringIO.new(nil)
+    assert_nil io.gets
+    io.puts "abc"
+    assert_nil io.string
+  end
+
   def test_truncate
     io = StringIO.new("")
     io.puts "abc"