diff --git a/ChangeLog b/ChangeLog
index 1c82985e4f..bb72f3b061 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Dec 19 10:52:29 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* bignum.c (rb_cstr_to_inum): an underscore succeeding after octal
+	  prefix is allowed.  [ruby-core:14139]
+
 Wed Dec 19 00:09:19 2007  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* bignum.c (rb_cstr_to_inum): wrong radix check.  a patch from
diff --git a/bignum.c b/bignum.c
index c840fe06f7..3f2db057af 100644
--- a/bignum.c
+++ b/bignum.c
@@ -439,7 +439,7 @@ rb_cstr_to_inum(const char *str, int base, int badcheck)
 	len = 2;
 	break;
       case 8:
-	if (str[0] == '0' && (str[1] == 'o'||str[1] == 'O')) {
+	if (str[0] == '0' && (str[1] == 'o'||str[1] == 'O'||str[1] == '_')) {
 	    str += 2;
 	}
       case 4: case 5: case 6: case 7:
diff --git a/test/ruby/test_integer.rb b/test/ruby/test_integer.rb
index 81f8c65797..db62a08cc4 100644
--- a/test/ruby/test_integer.rb
+++ b/test/ruby/test_integer.rb
@@ -670,5 +670,8 @@ class TestInteger < Test::Unit::TestCase
     assert_nothing_raised(ArgumentError, "[ruby-core:13873]") {
       assert_equal(0, Integer("0 "))
     }
+    assert_nothing_raised(ArgumentError, "[ruby-core:14139]") {
+      assert_equal(0377, Integer("0_3_7_7"))
+    }
   end
 end