diff --git a/include/functions2.php b/include/functions2.php
index c0ebcff83..ed22a0623 100644
--- a/include/functions2.php
+++ b/include/functions2.php
@@ -2048,7 +2048,9 @@
 	 * @return string Absolute URL
 	 */
 	function rewrite_relative_url($url, $rel_url) {
-		if (strpos($rel_url, "://") !== false) {
+		if (strpos($rel_url, ":") !== false) {
+			return $rel_url;
+		} else if (strpos($rel_url, "://") !== false) {
 			return $rel_url;
 		} else if (strpos($rel_url, "//") === 0) {
 			# protocol-relative URL (rare but they exist)