diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index 47ff270b76..e73f90a772 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -1999,6 +1999,12 @@ function append_sid($url, $params = false, $is_amp = true, $session_id = false)
 {
 	global $_SID, $_EXTRA_URL, $phpbb_hook;
 
+	if ($params === '' || (is_array($params) && empty($params)))
+	{
+		// Do not append the ? if the param-list is empty anyway.
+		$params = false;
+	}
+
 	// Developers using the hook function need to globalise the $_SID and $_EXTRA_URL on their own and also handle it appropriately.
 	// They could mimic most of what is within this function
 	if (!empty($phpbb_hook) && $phpbb_hook->call_hook(__FUNCTION__, $url, $params, $is_amp, $session_id))
diff --git a/tests/session/append_sid_test.php b/tests/session/append_sid_test.php
new file mode 100644
index 0000000000..1a3ad633e3
--- /dev/null
+++ b/tests/session/append_sid_test.php
@@ -0,0 +1,51 @@
+<?php
+/**
+*
+* @package testing
+* @copyright (c) 2011 phpBB Group
+* @license http://opensource.org/licenses/gpl-license.php GNU Public License
+*
+*/
+
+require_once dirname(__FILE__) . '/../../phpBB/includes/functions.php';
+
+class phpbb_session_append_sid_test extends phpbb_test_case
+{
+
+	public function append_sid_data()
+	{
+		return array(
+			array('viewtopic.php?t=1&amp;f=2', false, true, false, 'viewtopic.php?t=1&amp;f=2', 'parameters in url-argument'),
+			array('viewtopic.php', 't=1&amp;f=2', true, false, 'viewtopic.php?t=1&amp;f=2', 'parameters in params-argument using amp'),
+			array('viewtopic.php', 't=1&f=2', false, false, 'viewtopic.php?t=1&f=2', 'parameters in params-argument using &'),
+			array('viewtopic.php', array('t' => 1, 'f' => 2), true, false, 'viewtopic.php?t=1&amp;f=2', 'parameters in params-argument as array'),
+
+			// Custom sid parameter
+			array('viewtopic.php', 't=1&amp;f=2', true, 'custom-sid', 'viewtopic.php?t=1&amp;f=2&amp;sid=custom-sid', 'using session_id'),
+
+			// Testing anchors
+			array('viewtopic.php?t=1&amp;f=2#anchor', false, true, false, 'viewtopic.php?t=1&amp;f=2#anchor', 'anchor in url-argument'),
+			array('viewtopic.php', 't=1&amp;f=2#anchor', true, false, 'viewtopic.php?t=1&amp;f=2#anchor', 'anchor in params-argument'),
+			array('viewtopic.php', array('t' => 1, 'f' => 2, '#' => 'anchor'), true, false, 'viewtopic.php?t=1&amp;f=2#anchor', 'anchor in params-argument (array)'),
+
+			// Anchors and custom sid
+			array('viewtopic.php?t=1&amp;f=2#anchor', false, true, 'custom-sid', 'viewtopic.php?t=1&amp;f=2&amp;sid=custom-sid#anchor', 'anchor in url-argument using session_id'),
+			array('viewtopic.php', 't=1&amp;f=2#anchor', true, 'custom-sid', 'viewtopic.php?t=1&amp;f=2&amp;sid=custom-sid#anchor', 'anchor in params-argument using session_id'),
+			array('viewtopic.php', array('t' => 1, 'f' => 2, '#' => 'anchor'), true, 'custom-sid', 'viewtopic.php?t=1&amp;f=2&amp;sid=custom-sid#anchor', 'anchor in params-argument (array) using session_id'),
+
+			// Empty parameters should not append the ?
+			array('viewtopic.php', false, true, false, 'viewtopic.php', 'no params using bool false'),
+			array('viewtopic.php', '', true, false, 'viewtopic.php', 'no params using empty string'),
+			array('viewtopic.php', array(), true, false, 'viewtopic.php', 'no params using empty array'),
+		);
+	}
+
+	/**
+	* @dataProvider append_sid_data
+	*/
+	public function test_append_sid($url, $params, $is_amp, $session_id, $expected, $description)
+	{
+		$this->assertEquals($expected, append_sid($url, $params, $is_amp, $session_id));
+	}
+}
+