diff --git a/filter.php b/filter.php
index 38213314d0e81e0d80151b6860ee2f5b33eaeb1b..1a53e8f77b6adfb4e41cc8c046a0ef91e16ce174 100644
--- a/filter.php
+++ b/filter.php
@@ -68,7 +68,7 @@ class filter_opencast extends moodle_text_filter
                 $urlparts = parse_url($episodeurl);
                 $baseurl = $urlparts['scheme'] . '://' . $urlparts['host'];
                 if (isset($urlparts['port'])) {
-                    $baseurl .= $urlparts['port'];
+                    $baseurl .= ':' . $urlparts['port'];
                 }
 
                 if (empty($episodeurl) || stripos($text, $baseurl) === false) {