diff --git a/program/lib/Roundcube/rcube_config.php b/program/lib/Roundcube/rcube_config.php
index 9bce9dd3e..814ff88dc 100644
--- a/program/lib/Roundcube/rcube_config.php
+++ b/program/lib/Roundcube/rcube_config.php
@@ -594,7 +594,7 @@ class rcube_config
         $list = (array) $this->prop['keyservers'];
 
         foreach ($list as $idx => $host) {
-            if (!preg_match('|^[a-z]://|', $host)) {
+            if (!preg_match('|^[a-z]+://|', $host)) {
                 $host = "https://$host";
             }