diff -u b/config/install/exception_mailer.settings.yml b/config/install/exception_mailer.settings.yml
--- b/config/install/exception_mailer.settings.yml
+++ b/config/install/exception_mailer.settings.yml
@@ -2,4 +2,4 @@
-  emergency: 'emergency'
-  alert: 'alert'
-  critical: 'critical'
-  error: 'error'
+  0: '0'
+  1: '1'
+  2: '2'
+  3: '3'
diff -u b/src/Form/ExceptionMailerConfigForm.php b/src/Form/ExceptionMailerConfigForm.php
--- b/src/Form/ExceptionMailerConfigForm.php
+++ b/src/Form/ExceptionMailerConfigForm.php
@@ -4,7 +4,7 @@
 
 use Drupal\Core\Form\ConfigFormBase;
 use Drupal\Core\Form\FormStateInterface;
-use Psr\Log\LogLevel;
+use Drupal\Core\Logger\RfcLogLevel;
 
 /**
  * Class ExceptionMailerConfigForm.
@@ -35,16 +35,7 @@
     $form['level_type'] = [
       '#type' => 'checkboxes',
       '#title' => $this->t('Check the level type'),
-      '#options' => [
-        LogLevel::EMERGENCY => $this->t(LogLevel::EMERGENCY),
-        LogLevel::ALERT => $this->t(LogLevel::ALERT),
-        LogLevel::CRITICAL => $this->t(LogLevel::CRITICAL),
-        LogLevel::ERROR => $this->t(LogLevel::ERROR),
-        LogLevel::WARNING => $this->t(LogLevel::WARNING),
-        LogLevel::NOTICE => $this->t(LogLevel::NOTICE),
-        LogLevel::INFO => $this->t(LogLevel::INFO),
-        LogLevel::DEBUG => $this->t(LogLevel::DEBUG),
-      ],
+      '#options' => RfcLogLevel::getLevels(),
       '#default_value' => $config->get('level_type'),
     ];
     return parent::buildForm($form, $form_state);
@@ -57,7 +48,9 @@
     parent::submitForm($form, $form_state);
 
     $this->config('exception_mailer.settings')
-      ->set('level_type', array_filter($form_state->getValue('level_type')))
+      ->set('level_type', array_filter($form_state->getValue('level_type'), function($v) {
+        return $v !== 0;
+      }))
       ->save();
   }
 
diff -u b/src/Logger/ErrorLog.php b/src/Logger/ErrorLog.php
--- b/src/Logger/ErrorLog.php
+++ b/src/Logger/ErrorLog.php
@@ -13,7 +13,6 @@
 use Drupal\Core\Logger\RfcLogLevel;
 use Drupal\exception_mailer\Utility\UserRepository;
 use Drupal\Component\Utility\Xss;
-use Psr\Log\LogLevel;
 
 /**
  * Class ErrorLog.
@@ -87,45 +86,7 @@
     // style, so they can be translated too in runtime.
     $message_placeholders = $this->parser->parseMessagePlaceholders($message, $context);
 
-    $level_types = $this->configFactory->get('exception_mailer.settings')->get('level_type');
-    $level_types = array_filter($level_types);
-
-    $levels = [];
-    foreach ($level_types as $level_type) {
-      switch ($level_type) {
-        case LogLevel::EMERGENCY:
-          $levels[LogLevel::EMERGENCY] = RfcLogLevel::EMERGENCY;
-          break;
-
-        case LogLevel::ALERT:
-          $levels[LogLevel::ALERT] = RfcLogLevel::ALERT;
-          break;
-
-        case LogLevel::CRITICAL:
-          $levels[LogLevel::CRITICAL] = RfcLogLevel::CRITICAL;
-          break;
-
-        case LogLevel::ERROR:
-          $levels[LogLevel::ERROR] = RfcLogLevel::ERROR;
-          break;
-
-        case LogLevel::WARNING:
-          $levels[LogLevel::WARNING] = RfcLogLevel::WARNING;
-          break;
-
-        case LogLevel::NOTICE:
-          $levels[LogLevel::NOTICE] = RfcLogLevel::NOTICE;
-          break;
-
-        case LogLevel::INFO:
-          $levels[LogLevel::INFO] = RfcLogLevel::INFO;
-          break;
-
-        case LogLevel::DEBUG:
-          $levels[LogLevel::DEBUG] = RfcLogLevel::DEBUG;
-          break;
-      }
-    }
+    $levels = $this->configFactory->get('exception_mailer.settings')->get('level_type');
 
     if (empty($levels)) {
       return;
@@ -134,7 +95,8 @@
     $queue = $this->queueFactory->get('manual_exception_email', TRUE);
     $queue_worker = $this->queueManager->createInstance('manual_exception_email');
 
-    if (\in_array($level, array_values($levels), TRUE)) {
+    $severity = RfcLogLevel::getLevels();
+    if (\in_array($level, array_values($levels), FALSE)) {
       foreach (UserRepository::getUserEmails('administrator') as $admin) {
         $data['email'] = $admin;
         $data['exception'] = '';
@@ -142,7 +104,7 @@
         $data['site'] = $this->configFactory->get('system.site')->get('name');
         $data['timestamp'] = $context['timestamp'];
         $data['user'] = $context['uid'];
-        $data['severity'] = array_search($level, $levels, TRUE);
+        $data['severity'] = $severity[$level];
         $data['type'] = mb_substr($context['channel'], 0, 64);
         $data['link'] = $context['link'];
         $data['location'] = $context['request_uri'];