diff --git a/ChangeLog b/ChangeLog
index a0a586ebd8..35009540c0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Mar 29 15:10:39 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/tempfile.rb (Tempfile#open): re-open with same mode and
+	  options as initialize.
+
 Mon Mar 29 09:16:45 2010  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* random.c: change include order; ruby.h should be at first.
diff --git a/lib/tempfile.rb b/lib/tempfile.rb
index e1bccf0a90..79dd5cc02c 100755
--- a/lib/tempfile.rb
+++ b/lib/tempfile.rb
@@ -138,6 +138,7 @@ class Tempfile < DelegateClass(File)
       if opts
         mode |= opts.delete(:mode) || 0
         opts[:perm] = perm
+        perm = nil
       else
         opts = perm
       end
@@ -148,6 +149,9 @@ class Tempfile < DelegateClass(File)
       ensure
         self.class.rmdir(lock)
       end
+      @mode = mode & ~(File::CREAT|File::EXCL)
+      perm or opts.freeze
+      @opts = opts
     end
 
     super(@tmpfile)
@@ -156,7 +160,7 @@ class Tempfile < DelegateClass(File)
   # Opens or reopens the file with mode "r+".
   def open
     @tmpfile.close if @tmpfile
-    @tmpfile = File.open(@tmpname, 'r+')
+    @tmpfile = File.open(@tmpname, @mode, @opts)
     @data[1] = @tmpfile
     __setobj__(@tmpfile)
   end
diff --git a/test/test_tempfile.rb b/test/test_tempfile.rb
index 073a11e15a..e15d3f6a0c 100644
--- a/test/test_tempfile.rb
+++ b/test/test_tempfile.rb
@@ -294,6 +294,8 @@ puts Tempfile.new('foo').path
     t = tempfile("TEST", mode: IO::BINARY)
     if IO::BINARY.nonzero?
       assert(t.binmode?)
+      t.open
+      assert(t.binmode?, 'binmode after reopen')
     else
       assert_equal(0600, t.stat.mode & 0777)
     end