diff --git a/ChangeLog b/ChangeLog
index fef92b1a44..f93db948e4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Jul 12 11:44:23 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* string.c (rb_str_new_frozen): since the result object should have
+	  same tainted/untrusted bits with the original object, return new
+	  object if the shared object unmatch.  [ruby-core:39745][Bug #5374]
+
 Thu Jul 12 10:46:39 2012  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* test/net/http/test_http.rb (TestNetHTTPLocalBind#test_bind_to_local*):
diff --git a/string.c b/string.c
index 82c62e6a42..d038835c72 100644
--- a/string.c
+++ b/string.c
@@ -681,7 +681,7 @@ rb_str_new_frozen(VALUE orig)
 	assert(OBJ_FROZEN(str));
 	ofs = RSTRING_LEN(str) - RSTRING_LEN(orig);
 	if ((ofs > 0) || (klass != RBASIC(str)->klass) ||
-	    (!OBJ_TAINTED(str) && OBJ_TAINTED(orig)) ||
+	    ((RBASIC(str)->flags ^ RBASIC(orig)->flags) & (FL_TAINT|FL_UNTRUSTED)) ||
 	    ENCODING_GET(str) != ENCODING_GET(orig)) {
 	    str = str_new3(klass, str);
 	    RSTRING(str)->as.heap.ptr += ofs;
diff --git a/test/ruby/test_file.rb b/test/ruby/test_file.rb
index b0a6971e69..45c6efbd74 100644
--- a/test/ruby/test_file.rb
+++ b/test/ruby/test_file.rb
@@ -316,6 +316,16 @@ class TestFile < Test::Unit::TestCase
     end
   end
 
+  def test_untainted_path
+    bug5374 = '[ruby-core:39745]'
+    cwd = ("./"*40+".".taint).dup.untaint
+    in_safe = proc {|safe| $SAFE = safe; File.stat(cwd)}
+    assert_not_send([cwd, :tainted?])
+    (0..1).each do |level|
+      assert_nothing_raised(SecurityError, bug5374) {in_safe[level]}
+    end
+  end
+
   if /(bcc|ms|cyg)win|mingw|emx/ =~ RUBY_PLATFORM
     def test_long_unc
       feature3399 = '[ruby-core:30623]'