diff -u b/src/Form/SensorForm.php b/src/Form/SensorForm.php
--- b/src/Form/SensorForm.php
+++ b/src/Form/SensorForm.php
@@ -109,6 +109,12 @@
     );
 
     if (isset($sensor_config->plugin_id) && $plugin = $sensor_config->getPlugin()) {
+
+      // Set default configuration of the sensor.
+      if ($default_config = $plugin->getDefaultConfiguration()) {
+        $sensor_config->set('settings', $default_config);
+      }
+
       $form['plugin_container']['settings'] = array(
         '#type' => 'details',
         '#open' => TRUE,
@@ -237,10 +243,6 @@
       $plugin = $sensor_config->getPlugin();
     }
 
-    if ($default_config = $plugin->getDefaultConfiguration()) {
-      $form_state->setValue('settings', $default_config);
-    }
-
     $plugin->validateConfigurationForm($form, $form_state);
 
     if ($this->entity->isNumeric()) {