diff --git a/ChangeLog b/ChangeLog
index b3b59e291c..74a142a8c0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Wed Dec 24 14:23:27 2003  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/stringio/stringio.c (strio_read): clear the buffer argument
+	  when returning nil.  [ruby-dev:22363]
+
+	* test/ruby/ut_eof.rb (TestEOF::test_eof_0, TestEOF::test_eof_1):
+	  add buffer argument tests.
+
 Wed Dec 24 14:07:55 2003  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/test/unit/assertions.rb: Modules are allowed to rescue.
diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 1bab5b4d1f..8d3275b2b8 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -851,9 +851,11 @@ strio_read(argc, argv, self)
 	    }
 	    if (len > 0 && ptr->pos >= RSTRING(ptr->string)->len) {
 		ptr->flags |= STRIO_EOF;
+		if (!NIL_P(str)) rb_str_resize(str, 0);
 		return Qnil;
 	    }
 	    else if (ptr->flags & STRIO_EOF) {
+		if (!NIL_P(str)) rb_str_resize(str, 0);
 		return Qnil;
 	    }
 	    break;
diff --git a/test/ruby/ut_eof.rb b/test/ruby/ut_eof.rb
index 8b3cc8101b..eff0bddc0b 100644
--- a/test/ruby/ut_eof.rb
+++ b/test/ruby/ut_eof.rb
@@ -14,6 +14,16 @@ module TestEOF
       assert_equal("", f.read)
       assert_nil(f.read(1))
     }
+    open_file("") {|f|
+      s = "x"
+      assert_equal("", f.read(nil, s))
+      assert_equal("", s)
+    }
+    open_file("") {|f|
+      s = "x"
+      assert_nil(f.read(10, s))
+      assert_equal("", s)
+    }
   end
 
   def test_eof_0_rw
@@ -61,6 +71,16 @@ module TestEOF
       assert_equal("a", f.read)
       assert_nil(f.read(0))
     }
+    open_file("a") {|f|
+      s = "x"
+      assert_equal("a", f.read(nil, s))
+      assert_equal("a", s)
+    }
+    open_file("a") {|f|
+      s = "x"
+      assert_equal("a", f.read(10, s))
+      assert_equal("a", s)
+    }
   end
 
   module Seek