Unsupported operand type: string+string in eppc-ups.inc.php

#####  Module Start: os  #####

 o OS Poller            OS

PHP Fatal error:  Uncaught TypeError: Unsupported operand types: string + string in /opt/observium/includes/polling/os/eppc-ups.inc.php:23

Stack trace:

#0 /opt/observium/includes/polling/os.inc.php(157): include()

#1 /opt/observium/includes/polling/functions.inc.php(305): include('...')

#2 /opt/observium/poller.php(171): poll_device()

#3 {main}

  thrown in /opt/observium/includes/polling/os/eppc-ups.inc.php on line 23 

Index: includes/polling/os/eppc-ups.inc.php

===================================================================

--- includes/polling/os/eppc-ups.inc.php	(revision 12246)

+++ includes/polling/os/eppc-ups.inc.php	(working copy)

@@ -20,7 +20,7 @@

     $hardware = snmp_get($device, 'upsEIdentityManufacturer.0', '-OQv', 'EPPC-MIB') . ' (' .

                 snmp_get($device, 'upsESystemConfigOutputVA.0', '-OQv', 'EPPC-MIB') . 'VA ' . snmp_get($device, 'upsEIdentityModel.0', '-OQv', 'EPPC-MIB') . ')';

     $upsEIdentityDescription = snmp_get($device, 'upsEIdentityDescription.0', '-OQv', 'EPPC-MIB');

-    $version = $upsEIdentityDescription + ' UPS: ' .

+    $version = $upsEIdentityDescription . ' UPS: ' .

                snmp_get($device, 'upsEIdentityUPSFirmwareVerison.0', '-OQv', 'EPPC-MIB') . ' Firmware: ' . snmp_get($device, 'upsIdentAgentSoftwareVersion.0', '-OQv', 'EPPC-MIB');

     $status = snmp_get($device, 'upsESystemStatus.0', '-OQv', 'EPPC-MIB') . ' ' . snmp_get($device, 'upsEBatteryTestResult.0', '-OQv', 'EPPC-MIB');