diff --git a/system/core/Config.php b/system/core/Config.php
index 3de1bcb..6563827 100644
--- a/system/core/Config.php
+++ b/system/core/Config.php
@@ -225,12 +225,12 @@
 	 * Site URL
 	 * Returns base_url . index_page [. uri_string]
 	 *
-	 * @param	string	the URI string
+	 * @param	mixed	the URI string or an array of segments
 	 * @return	string
 	 */
 	public function site_url($uri = '')
 	{
-		if ($uri === '')
+		if (empty($uri))
 		{
 			return $this->slash_item('base_url').$this->item('index_page');
 		}
@@ -240,10 +240,12 @@
 			$suffix = ($this->item('url_suffix') === FALSE) ? '' : $this->item('url_suffix');
 			return $this->slash_item('base_url').$this->slash_item('index_page').$this->_uri_string($uri).$suffix;
 		}
-		else
+		elseif (is_array($uri) OR strpos($uri, '?') === FALSE)
 		{
-			return $this->slash_item('base_url').$this->item('index_page').'?'.$this->_uri_string($uri);
+			$uri = '?'.$this->_uri_string($uri);
 		}
+
+		return $this->slash_item('base_url').$this->item('index_page').$uri;
 	}
 
 	// -------------------------------------------------------------
@@ -280,15 +282,7 @@
 		}
 		elseif (is_array($uri))
 		{
-			$i = 0;
-			$str = '';
-			foreach ($uri as $key => $val)
-			{
-				$prefix = ($i === 0) ? '' : '&';
-				$str .= $prefix.$key.'='.$val;
-				$i++;
-			}
-			return $str;
+			return http_build_query($uri);
 		}
 
 		return $uri;
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index b3c2e70..b9d7264 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -163,12 +163,12 @@
 
 -  Core
 
-   -  Changed private functions in CI_URI to protected so MY_URI can override them.
+   -  Changed private methods in the :doc:`URI Library <libraries/uri>` to protected so MY_URI can override them.
    -  Removed CI_CORE boolean constant from CodeIgniter.php (no longer Reactor and Core versions).
-   -  Added method get_vars() to CI_Loader to retrieve all variables loaded with $this->load->vars().
+   -  Added method get_vars() to the :doc:`Loader Library <libraries/loader>` to retrieve all variables loaded with $this->load->vars().
    -  is_loaded() function from system/core/Commons.php now returns a reference.
    -  $config['rewrite_short_tags'] now has no effect when using PHP 5.4 as *<?=* will always be available.
-   -  Added method() to CI_Input to retrieve $_SERVER['REQUEST_METHOD'].
+   -  Added method() to the :doc:`Input Library <libraries/input>` to retrieve $_SERVER['REQUEST_METHOD'].
    -  Modified valid_ip() to use PHP's filter_var() in the :doc:`Input Library <libraries/input>`.
    -  Added support for HTTP-Only cookies with new config option ``cookie_httponly`` (default FALSE).
    -  Renamed method _call_hook() to call_hook() in the :doc:`Hooks Library <general/hooks>`.
@@ -177,6 +177,7 @@
    -  Added a second argument to set_content_type() in the :doc:`Output Library <libraries/output>` that allows setting the document charset as well.
    -  $config['time_reference'] now supports all timezone strings supported by PHP.
    -  Added support for HTTP code 303 ("See Other") in set_status_header().
+   -  Changed :doc:`Config Library <libraries/config>` method site_url() to accept an array as well.
 
 Bug fixes for 3.0
 ------------------
@@ -276,6 +277,7 @@
 -  Fixed a bug (#520) - :doc:`Date Helper <helpers/date_helper>` function nice_date() failed when the optional second parameter is not passed.
 -  Fixed a bug (#167) - ``$config['permitted_uri_chars']`` didn't affect URL-encoded characters.
 -  Fixed a bug (#318) - :doc:`Profiling <general/profiling>` setting *query_toggle_count* was not settable as described in the manual.
+-  Fixed a bug (#938) - :doc:`Config Library <libraries/config>` method site_url() added a question mark to the URL string when query strings are enabled even if it already existed.
 
 Version 2.1.1
 =============
diff --git a/user_guide_src/source/libraries/config.rst b/user_guide_src/source/libraries/config.rst
index 08d9c29..6948963 100644
--- a/user_guide_src/source/libraries/config.rst
+++ b/user_guide_src/source/libraries/config.rst
@@ -175,7 +175,7 @@
 as to a stylesheet or image.
 
 The two functions above are normally accessed via the corresponding
-functions in the :doc:`URL Helper </helpers/url_helper>`.
+functions in the :doc:`URL Helper <helpers/url_helper>`.
 
 $this->config->system_url();
 *****************************