diff --git a/core/lib/Drupal/Core/Database/Query/Condition.php b/core/lib/Drupal/Core/Database/Query/Condition.php
index 51693576e8..891b7e910b 100644
--- a/core/lib/Drupal/Core/Database/Query/Condition.php
+++ b/core/lib/Drupal/Core/Database/Query/Condition.php
@@ -4,6 +4,7 @@
 
 use Drupal\Core\Database\Connection;
 use Drupal\Core\Database\InvalidQueryException;
+use Drupal\Core\Site\Settings;
 
 /**
  * Generic class for a series of conditions in a query.
@@ -243,6 +244,9 @@ public function compile(Connection $connection, PlaceholderInterface $queryPlace
             // broken.
             // On top of that the database API relies on __toString() which
             // does not allow to throw exceptions.
+            if (Settings::get('development_mode', FALSE)) {
+              throw new \InvalidArgumentException('Invalid characters in query operator: ' . $condition['operator']);
+            }
             trigger_error('Invalid characters in query operator: ' . $condition['operator'], E_USER_ERROR);
             return;
           }
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index ce48afe725..1be741df94 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -872,6 +872,15 @@ function system_requirements($phase) {
     }
     $requirements['update status']['title'] = t('Update notifications');
 
+    if (Settings::get('development_mode', FALSE)) {
+      $requirements['development_mode'] = [
+        'title' => t('Development mode'),
+        'value' => t('Enabled'),
+        'severity' => REQUIREMENT_WARNING,
+        'description' => t('Development mode is enabled in settings.php. It is recommended to have this setting disabled in production environments.'),
+      ];
+    }
+
     if (Settings::get('rebuild_access')) {
       $requirements['rebuild access'] = [
         'title' => t('Rebuild access'),
diff --git a/sites/example.settings.local.php b/sites/example.settings.local.php
index 330be144c5..9dacb19818 100644
--- a/sites/example.settings.local.php
+++ b/sites/example.settings.local.php
@@ -115,3 +115,15 @@
  * directory.
  */
 $settings['skip_permissions_hardening'] = TRUE;
+
+/**
+ * Development mode:
+ *
+ * This setting can be set to TRUE to enable more verbose error messages. We try
+ * for example to not only log errors, but also show them in development mode.
+ * This is unrelated with development specific settings, like disabled twig
+ * caching or aggregated css and JS.
+ *
+ * Not recommended in production environments.
+ */
+# $settings['development_mode'] = TRUE;