diff --git a/plugins/acl/acl.php b/plugins/acl/acl.php
index 35a92bb1c..384faa3b7 100644
--- a/plugins/acl/acl.php
+++ b/plugins/acl/acl.php
@@ -123,7 +123,7 @@ class acl extends rcube_plugin
                     $group_id = is_array($record[$group_field]) ? $record[$group_field][0] : $record[$group_field];
 
                     if ($group) {
-                        $users[] = array('name' => ($prefix ? $prefix : '') . $group_id, 'display' => $group);
+                        $users[] = array('name' => ($prefix ? $prefix : '') . $group_id, 'display' => $group, 'type' => 'group');
                         $keys[]  = $group;
                     }
                 }
diff --git a/program/lib/Roundcube/rcube_db_mysql.php b/program/lib/Roundcube/rcube_db_mysql.php
index 0e85b0f9c..067e94be6 100644
--- a/program/lib/Roundcube/rcube_db_mysql.php
+++ b/program/lib/Roundcube/rcube_db_mysql.php
@@ -161,15 +161,24 @@ class rcube_db_mysql extends rcube_db
     {
         if (!isset($this->variables)) {
             $this->variables = array();
+        }
 
-            $result = $this->query('SHOW VARIABLES');
+        if (array_key_exists($varname, $this->variables)) {
+            return $this->variables[$varname];
+        }
 
-            while ($row = $this->fetch_array($result)) {
-                $this->variables[$row[0]] = $row[1];
-            }
+        $result = $this->query('SHOW VARIABLES LIKE ?', $varname);
+
+        while ($row = $this->fetch_array($result)) {
+            $this->variables[$row[0]] = $row[1];
+        }
+
+        // not found, use default
+        if (!isset($this->variables[$varname])) {
+            $this->variables[$varname] = $default;
         }
 
-        return isset($this->variables[$varname]) ? $this->variables[$varname] : $default;
+        return $this->variables[$varname];
     }
 
     /**
diff --git a/program/steps/mail/get.inc b/program/steps/mail/get.inc
index 02ec5a4ac..5803e0c5a 100644
--- a/program/steps/mail/get.inc
+++ b/program/steps/mail/get.inc
@@ -164,7 +164,7 @@ else if (strlen($part_id)) {
                 else {
                     // get valid file extensions
                     $extensions      = rcube_mime::get_mime_extensions($real_mimetype);
-                    $valid_extension = !$file_extension || in_array($file_extension, (array)$extensions);
+                    $valid_extension = !$file_extension || empty($extensions) || in_array($file_extension, (array)$extensions);
                 }
 
                 // fix mimetype for images wrongly declared as octet-stream