diff --git a/html/includes/functions.inc.php b/html/includes/functions.inc.php
index ad4df7734..66bfe70a0 100644
--- a/html/includes/functions.inc.php
+++ b/html/includes/functions.inc.php
@@ -26,7 +26,7 @@ function generate_device_link($device, $text=0, $linksuffix="", $start=0, $end=0
   {
     $graphs = $config['os'][$device['os']]['over'];
   }
-  elseif (isset($config['os'][$device['os_group']]['over']))
+  elseif (isset($device['os_group']) && isset($config['os'][$device['os_group']]['over']))
   {
     $graphs = $config['os'][$device['os_group']]['over'];
   }
@@ -244,7 +244,7 @@ function generate_port_link($args, $text = NULL, $type = NULL)
   $args = ifNameDescr($args);
   if (!$text) { $text = fixIfName($args['label']); }
   if ($type) { $args['graph_type'] = $type; }
-  if (!$args['graph_type']) { $args['graph_type'] = 'port_bits'; }
+  if (!isset($args['graph_type'])) { $args['graph_type'] = 'port_bits'; }
 
   $class = ifclass($args['ifOperStatus'], $args['ifAdminStatus']);
   if (!isset($args['hostname'])) { $args = array_merge($args, device_by_id_cache($args['device_id'])); }
diff --git a/html/index.php b/html/index.php
index 5cd429081..57f2bcec7 100755
--- a/html/index.php
+++ b/html/index.php
@@ -33,7 +33,7 @@ $month = time() - (31 * 24 * 60 * 60);
 $year = time() - (365 * 24 * 60 * 60);
 
 # Load the settings for Multi-Tenancy.
-if (is_array($config['branding']))
+if (isset($config['branding']) && is_array($config['branding']))
 {
   if ($config['branding'][$_SERVER['SERVER_NAME']])
   {
diff --git a/includes/common.php b/includes/common.php
index 2dc3d42bb..649cad106 100644
--- a/includes/common.php
+++ b/includes/common.php
@@ -100,7 +100,7 @@ function device_by_id_cache($device_id)
 {
   global $device_cache;
 
-  if (is_array($device_cache[$device_id]))
+  if (isset($device_cache[$device_id]) && is_array($device_cache[$device_id]))
   {
     $device = $device_cache[$device_id];
   } else {