diff --git a/lib/Cake/Test/Case/View/Helper/TextHelperTest.php b/lib/Cake/Test/Case/View/Helper/TextHelperTest.php
index d38d60529..9a3eba7cb 100644
--- a/lib/Cake/Test/Case/View/Helper/TextHelperTest.php
+++ b/lib/Cake/Test/Case/View/Helper/TextHelperTest.php
@@ -265,6 +265,10 @@ class TextHelperTest extends CakeTestCase {
 				'Text with a url http://www.not--work.com and more',
 				'Text with a url <a href="http://www.not--work.com">http://www.not--work.com</a> and more',
 			),
+			array(
+				'Text with a url http://www.sub_domain.domain.pl and more',
+				'Text with a url <a href="http://www.sub_domain.domain.pl">http://www.sub_domain.domain.pl</a> and more',
+			),
 			array(
 				'Text with a partial www.küchenschöhn-not-working.de URL',
 				'Text with a partial <a href="http://www.küchenschöhn-not-working.de">www.küchenschöhn-not-working.de</a> URL'
diff --git a/lib/Cake/View/Helper/TextHelper.php b/lib/Cake/View/Helper/TextHelper.php
index 451aa17b6..17ed5a4eb 100644
--- a/lib/Cake/View/Helper/TextHelper.php
+++ b/lib/Cake/View/Helper/TextHelper.php
@@ -104,7 +104,7 @@ class TextHelper extends AppHelper {
 		$this->_placeholders = array();
 		$options += array('escape' => true);
 
-		$pattern = '#(?<!href="|src="|">)((?:https?|ftp|nntp)://[\p{L}0-9.\-:]+(?:[/?][^\s<]*)?)#ui';
+		$pattern = '#(?<!href="|src="|">)((?:https?|ftp|nntp)://[\p{L}0-9.\-_:]+(?:[/?][^\s<]*)?)#ui';
 		$text = preg_replace_callback(
 			$pattern,
 			array(&$this, '_insertPlaceHolder'),