diff --git a/plugins/system/sef/sef.php b/plugins/system/sef/sef.php
index e7c0307be54e5..e6b9185c73eb6 100644
--- a/plugins/system/sef/sef.php
+++ b/plugins/system/sef/sef.php
@@ -137,12 +137,14 @@ public function onAfterRender()
 				$regex,
 				function ($match) use ($base, $protocols)
 				{
-					$data = array();
-					foreach (explode(",", $match[1]) as $url)
+					preg_match_all('#(?:[^\s]+)\s*(?:[\d\.]+[wx])?(?:\,\s*)?#i', $match[1], $matches);
+
+					foreach ($matches[0] as &$src)
 					{
-						$data[] = preg_replace('#^(?!/|' . $protocols . '|\#|\')(.+)#', $base . '$1', trim($url));
+    						$src = preg_replace('#^(?!/|' . $protocols . '|\#|\')(.+)#', $base . '$1', $src);
 					}
-					return ' srcset="' . implode(",", $data) . '"';
+
+					return ' srcset="' . implode($matches[0]) . '"';
 				},
 				$buffer
 			);