diff --git a/src/Plugin/monitoring/SensorPlugin/DatabaseAggregatorSensorPlugin.php b/src/Plugin/monitoring/SensorPlugin/DatabaseAggregatorSensorPlugin.php
index 102d3b8..52d19fc 100644
--- a/src/Plugin/monitoring/SensorPlugin/DatabaseAggregatorSensorPlugin.php
+++ b/src/Plugin/monitoring/SensorPlugin/DatabaseAggregatorSensorPlugin.php
@@ -359,10 +359,11 @@ class DatabaseAggregatorSensorPlugin extends DatabaseAggregatorSensorPluginBase
       $form_state->set('fields_rows', count($fields) + 1);
     }
     for ($i = 0; $i < $form_state->get('fields_rows'); $i++) {
-      $form['output_table']['verbose_fields'][$i] = array(
+      $field = isset($fields[$i]) ? $fields[$i] : $i;
+      $form['output_table']['verbose_fields'][$field] = array(
         'field' => array(
           '#type' => 'textfield',
-          '#default_value' => isset($fields[$i]) ? $fields[$i] : '',
+          '#default_value' => (is_int($field)) ? '' : $field,
           '#title' => t('Field'),
           '#title_display' => 'invisible',
           '#size' => 20,
@@ -428,8 +429,8 @@ class DatabaseAggregatorSensorPlugin extends DatabaseAggregatorSensorPluginBase
 
     $verbose_fields = [];
     foreach ($form_state->getValue('verbose_fields') as $field) {
-      if (!empty($field)) {
-        $verbose_fields[] = $field;
+      if (!empty($field['field'])) {
+        $verbose_fields[] = $field['field'];
       }
     }
     $settings = $this->sensorConfig->getSettings();
@@ -530,29 +531,23 @@ class DatabaseAggregatorSensorPlugin extends DatabaseAggregatorSensorPluginBase
           t('The specified time interval field %name does not exist in table %table.', array('%name' => $field_name, $table)));
       }
     }
+
+    // Validate verbose_fields.
     $fields = $form_state->getValue('verbose_fields');
-    $new_fields = [];
     foreach ($fields as $key => $field) {
       $query = $database->select($table);
       $field_name = $field['field'];
-      if (!empty($field_name)) {
+      if (!empty($field_name) && !$database->schema()->fieldExists($table, $field_name)) {
         $query->addField($table, $field_name);
-        $new_fields[] = (array_pop($fields[$key]));
-        if (!$database->schema()->fieldExists($table, $field_name)) {
-          try {
-            $query->range(0, 1)->execute();
-          }
-          catch (\Exception $e) {
-
-            $form_state->setErrorByName("verbose_fields][$key][field", t('The field %field does not exist in the table "%table".', ['%field' => $new_fields[$key], '%table' => $table]));
-            unset($new_fields[$key]);
-            continue;
-          }
+        try {
+          $query->range(0, 1)->execute();
+        }
+        catch (\Exception $e) {
+          $form_state->setErrorByName("verbose_fields][$key][field", t('The field %field does not exist in the table "%table".', ['%field' => $field_name, '%table' => $table]));
+          continue;
         }
       }
     }
-
-    $form_state->setValue('verbose_fields', $new_fields);
   }
 
 }