diff --git a/wp-includes/formatting.php b/wp-includes/formatting.php
index 25e7fc1cbc..cb23ab50bb 100644
--- a/wp-includes/formatting.php
+++ b/wp-includes/formatting.php
@@ -1080,12 +1080,15 @@ function clean_url( $url, $protocols = null ) {
 	$original_url = $url;
 
 	if ('' == $url) return $url;
-	$url = preg_replace('|[^a-z0-9-~+_.?#=!&;,/:%]|i', '', $url);
+	$url = preg_replace('|[^a-z0-9-~+_.?#=!&;,/:%@]|i', '', $url);
 	$strip = array('%0d', '%0a');
 	$url = str_replace($strip, '', $url);
 	$url = str_replace(';//', '://', $url);
-	// Append http unless a relative link starting with / or a php file.
-	if ( strpos($url, '://') === false &&
+	/* If the URL doesn't appear to contain a scheme, we
+	 * presume it needs http:// appended (unless a relative 
+	 * link starting with / or a php file).
+	*/
+	if ( strpos($url, ':') === false &&
 		substr( $url, 0, 1 ) != '/' && !preg_match('/^[a-z0-9-]+?\.php/i', $url) )
 		$url = 'http://' . $url;