diff --git a/ChangeLog b/ChangeLog
index db5d690b31..a336719f8e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Mar 22 11:14:10 2012  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* test/ruby/test_io.rb (TestIO#test_pos_with_getc): updated.
+	  see [ruby-core:43550]
+
 Wed Mar 21 17:57:57 2012  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* regcomp.c: Merge Onigmo 3d855b30d574536d3ae600260208c6624ae4791c.
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index a3ac12765c..6990de1862 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -1360,21 +1360,23 @@ class TestIO < Test::Unit::TestCase
   def test_pos_with_getc
     bug6179 = '[ruby-core:43497]'
     t = make_tempfile
-    open(t.path, "w") do |f|
-      f.write "0123456789"
-    end
+    ["", "t", "b"].each do |mode|
+      open(t.path, "w#{mode}") do |f|
+        f.write "0123456789\n"
+      end
 
-    open(t.path, "r") do |f|
-      assert_equal 0, f.pos
-      assert_equal '0', f.getc
-      assert_equal 1, f.pos
-      assert_equal '1', f.getc
-      assert_equal 2, f.pos
-      assert_equal '2', f.getc
-      assert_equal 3, f.pos
-      assert_equal '3', f.getc
-      assert_equal 4, f.pos
-      assert_equal '4', f.getc
+      open(t.path, "r#{mode}") do |f|
+        assert_equal 0, f.pos, "mode=r#{mode}"
+        assert_equal '0', f.getc, "mode=r#{mode}"
+        assert_equal 1, f.pos, "mode=r#{mode}"
+        assert_equal '1', f.getc, "mode=r#{mode}"
+        assert_equal 2, f.pos, "mode=r#{mode}"
+        assert_equal '2', f.getc, "mode=r#{mode}"
+        assert_equal 3, f.pos, "mode=r#{mode}"
+        assert_equal '3', f.getc, "mode=r#{mode}"
+        assert_equal 4, f.pos, "mode=r#{mode}"
+        assert_equal '4', f.getc, "mode=r#{mode}"
+      end
     end
   end