diff --git a/ChangeLog b/ChangeLog
index d90b777bb0..0fb9ab9b49 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Tue Dec 23 19:42:59 2003  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* io.c (rb_io_ungetc): raise an exception at unread stream to
+	  avoid unspecified behavior.  [ruby-dev:22330]
+
+	* test/ruby/test_system.rb (test_syntax): glob relatively from
+	  __FILE__.
+
 Tue Dec 23 18:09:40 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* pack.c (pack_pack): remove unnecessary negative value check.
@@ -27,7 +35,7 @@ Tue Dec 23 14:13:51 2003  akira yamada  <akira@ruby-lang.org>
 
 	* test/uri/test_generic.rb (TestGeneric::test_set_component):
 	  added tets.
-	
+
 Tue Dec 23 11:08:34 2003  NAKAMURA, Hiroshi  <nahi@ruby-lang.org>
 
 	* test/xsd/test_noencoding.rb: rescue Errno::EINVAL and do not test.
diff --git a/io.c b/io.c
index 87caa7651f..8ecf0c1426 100644
--- a/io.c
+++ b/io.c
@@ -1314,8 +1314,9 @@ rb_io_ungetc(io, c)
     int cc = NUM2INT(c);
 
     GetOpenFile(io, fptr);
+    if (!(fptr->mode & FMODE_RBUF))
+	rb_raise(rb_eIOError, "unread stream");
     rb_io_check_readable(fptr);
-    flush_before_seek(fptr);
 
     if (ungetc(cc, fptr->f) == EOF && cc != EOF)
 	rb_sys_fail(fptr->path);
@@ -3456,7 +3457,7 @@ rb_io_ctl(io, req, arg, io_p)
 	rb_raise(rb_eArgError, "return value overflowed string");
     }
 
-   if (fptr->f2 && fileno(fptr->f) != fileno(fptr->f2)) {
+    if (fptr->f2 && fileno(fptr->f) != fileno(fptr->f2)) {
 	/* call on f2 too; ignore result */
 	io_cntl(fileno(fptr->f2), cmd, narg, io_p);
     }
diff --git a/test/ruby/test_system.rb b/test/ruby/test_system.rb
index 71eb7ad183..a19f6ef9b7 100644
--- a/test/ruby/test_system.rb
+++ b/test/ruby/test_system.rb
@@ -54,15 +54,11 @@ class TestSystem < Test::Unit::TestCase
 
     File.unlink "script_tmp" or `/bin/rm -f "script_tmp"`
     File.unlink "script_tmp.bak" or `/bin/rm -f "script_tmp.bak"`
+  end
 
-    if (dir = File.dirname(File.dirname($0))) == '.'
-      dir = ""
-    else
-      dir << "/"
-    end
-
+  def test_syntax
     assert_nothing_raised(Exception) do
-      for script in Dir["#{dir}{lib,sample,ext}/**/*.rb"]
+      for script in Dir[File.expand_path("../../../{lib,sample,ext}/**/*.rb", __FILE__)]
         valid_syntax? IO::read(script), script
       end
     end