diff --git a/ChangeLog b/ChangeLog
index 0ae387bed6..cfc2d47647 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Nov 18 20:46:08 2012  Tadayoshi Funaba  <tadf@dotrb.org>
+
+	* bignum.c (rb_cstr_to_inum): should accept underscores of
+	  sequence of two or more when unchecked mode.
+
 Sun Nov 18 16:33:00 2012  Naohisa Goto  <ngotogenome@gmail.com>
 
 	* configure.in, Makefile.in, common.mk: support DTrace on Solaris 10,
diff --git a/bignum.c b/bignum.c
index 97be53faf1..b6e551b837 100644
--- a/bignum.c
+++ b/bignum.c
@@ -733,7 +733,8 @@ rb_cstr_to_inum(const char *str, int base, int badcheck)
 		if (badcheck) goto bad;
 		break;
 	    }
-	    nondigit = (char) c;
+	    if (badcheck)
+		nondigit = (char) c;
 	    continue;
 	}
 	else if ((c = conv_digit(c)) < 0) {
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 2beaef3504..9f63847da3 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -1513,7 +1513,7 @@ class TestString < Test::Unit::TestCase
     assert_equal(12, "1_2".to_i(10))
     assert_equal(0x40000000, "1073741824".to_i(10))
     assert_equal(0x4000000000000000, "4611686018427387904".to_i(10))
-    assert_equal(1, "1__2".to_i(10))
+    assert_equal(12, "1__2".to_i(10))
     assert_equal(1, "1_z".to_i(10))
 
     bug6192 = '[ruby-core:43566]'