diff --git a/ChangeLog b/ChangeLog
index f8a1973bcf..d1212ff801 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Wed Sep 17 13:42:59 2008  Takeyuki Fujioka  <xibbar@ruby-lang.org>
+
+	* lib/cgi/html.rb (checkbox_group,radio_group): bug fix
+	  use size instead of	bytesize.
+
+	* test/cgi/test_cgi_tag_helper.rb: test for checkbox_group,radio_group.
+
 Wed Sep 17 06:58:31 2008  Tadayoshi Funaba  <tadf@dotrb.org>
 
 	* numeric.c: provides predicate real? instead of scalar?.
diff --git a/lib/cgi/html.rb b/lib/cgi/html.rb
index abc83cd23a..23d5ae9bea 100644
--- a/lib/cgi/html.rb
+++ b/lib/cgi/html.rb
@@ -248,12 +248,12 @@ class CGI
         if value.kind_of?(String)
           checkbox(name, value) + value
         else
-          if value[value.bytesize - 1] == true
+          if value[value.size - 1] == true
             checkbox(name, value[0], true) +
-            value[value.bytesize - 2]
+            value[value.size - 2]
           else
             checkbox(name, value[0]) +
-            value[value.bytesize - 1]
+            value[value.size - 1]
           end
         end
       }.join
@@ -703,12 +703,12 @@ class CGI
         if value.kind_of?(String)
           radio_button(name, value) + value
         else
-          if value[value.bytesize - 1] == true
+          if value[value.size - 1] == true
             radio_button(name, value[0], true) +
-            value[value.bytesize - 2]
+            value[value.size - 2]
           else
             radio_button(name, value[0]) +
-            value[value.bytesize - 1]
+            value[value.size - 1]
           end
         end
       }.join
diff --git a/test/cgi/test_cgi_tag_helper.rb b/test/cgi/test_cgi_tag_helper.rb
index 3ff2f54d42..38533a11e8 100755
--- a/test/cgi/test_cgi_tag_helper.rb
+++ b/test/cgi/test_cgi_tag_helper.rb
@@ -305,6 +305,14 @@ class CGITagHelperTest < Test::Unit::TestCase
     assert_equal('<TH>foo</TH>',cgi.th{'foo'})
     assert_equal('<TD>',cgi.td)
     assert_equal('<TD>foo</TD>',cgi.td{'foo'})
+    str=cgi.checkbox_group("foo",["aa","bb"],["cc","dd"])
+    assert_match(/^<INPUT .*VALUE="aa".*>bb<INPUT .*VALUE="cc".*>dd$/,str)
+    assert_match(/^<INPUT .*TYPE="checkbox".*>bb<INPUT .*TYPE="checkbox".*>dd$/,str)
+    assert_match(/^<INPUT .*NAME="foo".*>bb<INPUT .*NAME="foo".*>dd$/,str)
+    str=cgi.radio_group("foo",["aa","bb"],["cc","dd"])
+    assert_match(/^<INPUT .*VALUE="aa".*>bb<INPUT .*VALUE="cc".*>dd$/,str)
+    assert_match(/^<INPUT .*TYPE="radio".*>bb<INPUT .*TYPE="radio".*>dd$/,str)
+    assert_match(/^<INPUT .*NAME="foo".*>bb<INPUT .*NAME="foo".*>dd$/,str)
   end
   
 =begin