diff --git a/system/helpers/url_helper.php b/system/helpers/url_helper.php
index f6fb7d9..489f2d4 100644
--- a/system/helpers/url_helper.php
+++ b/system/helpers/url_helper.php
@@ -393,7 +393,7 @@
 	function auto_link($str, $type = 'both', $popup = FALSE)
 	{
 		// Find and replace any URLs.
-		if ($type !== 'email' && preg_match_all('#(\w*://|www\.)[^\s()<>;]+\w/?#i', $str, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER))
+		if ($type !== 'email' && preg_match_all('#(\w*://|www\.)[a-z0-9]+(-+[a-z0-9]+)*(\.[a-z0-9]+(-+[a-z0-9]+)*)+(/([^\s()<>;]+\w)?/?)?#i', $str, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER))
 		{
 			// Set our target HTML if using popup links.
 			$target = ($popup) ? ' target="_blank"' : '';
diff --git a/tests/codeigniter/helpers/url_helper_test.php b/tests/codeigniter/helpers/url_helper_test.php
index 5fbc364..83a8c0e 100644
--- a/tests/codeigniter/helpers/url_helper_test.php
+++ b/tests/codeigniter/helpers/url_helper_test.php
@@ -77,4 +77,13 @@
 		}
 	}
 
+	// --------------------------------------------------------------------
+
+	public function test_issue_5331()
+	{
+		$this->assertEquals(
+			'this is some text that includes '.safe_mailto('www.email@domain.com').' which is causing an issue',
+			auto_link('this is some text that includes www.email@domain.com which is causing an issue')
+		);
+	}
 }
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index eb879c5..1641f7c 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -21,6 +21,7 @@
 -  Fixed a bug (#5278) - :doc:`URL Helper <helpers/url_helper>` function :php:func:`auto_link()` didn't detect trailing slashes in URLs.
 -  Fixed a regression (#5282) - :doc:`Query Builder <database/query_builder>` method ``count_all_results()`` breaks ``ORDER BY`` clauses for subsequent queries.
 -  Fixed a bug (#5279) - :doc:`Query Builder <database/query_builder>` didn't account for already escaped identifiers while applying database name prefixes.
+-  Fixed a bug (#5331) - :doc:`URL Helper <helpers/url_helper>` function :php:func:`auto_link()` converted e-mail addresses starting with 'www.' to both "url" and "email" links.
 
 Version 3.1.6
 =============