diff --git a/html/pages/device.inc.php b/html/pages/device.inc.php
index b5719f4ae0..4d05e24933 100644
--- a/html/pages/device.inc.php
+++ b/html/pages/device.inc.php
@@ -397,7 +397,12 @@ if (device_permitted($vars['device']) || $permitted_by_port) {
                     $nfsensuffix = $config['nfsen_suffix'];
                 }
 
-                $basefilename_underscored = preg_replace('/\./', $config['nfsen_split_char'], $device['hostname']);
+                if (isset($config['nfsen_split_char']) && !empty($config['nfsen_split_char'])) {
+                    $basefilename_underscored = preg_replace('/\./', $config['nfsen_split_char'], $device['hostname']);
+                } else {
+                    $basefilename_underscored = $device['hostname'];
+                }
+
                 $nfsen_filename           = preg_replace('/'.$nfsensuffix.'/', '', $basefilename_underscored);
                 if (is_file($nfsenrrds.$nfsen_filename.'.rrd')) {
                     $nfsen_rrd_file = $nfsenrrds.$nfsen_filename.'.rrd';