diff --git a/core/modules/dblog/src/Controller/DbLogController.php b/core/modules/dblog/src/Controller/DbLogController.php
index c61e501..ae2fa71 100644
--- a/core/modules/dblog/src/Controller/DbLogController.php
+++ b/core/modules/dblog/src/Controller/DbLogController.php
@@ -17,6 +17,7 @@
 use Drupal\user\Entity\User;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Drupal\Core\Link;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 
 /**
  * Returns responses for dblog routes.
@@ -242,6 +243,9 @@ public function overview() {
    * @return array
    *   If the ID is located in the Database Logging table, a build array in the
    *   format expected by \Drupal\Core\Render\RendererInterface::render().
+   *
+   * @throws \Symfony\Component\HttpKernel\Exception\NotFoundHttpException
+   *   If no event found for the given ID.
    */
   public function eventDetails($event_id) {
     $build = [];
@@ -299,6 +303,9 @@ public function eventDetails($event_id) {
         ],
       ];
     }
+    else {
+      throw new NotFoundHttpException();
+    }
 
     return $build;
   }
diff --git a/core/modules/dblog/tests/src/Functional/DbLogTest.php b/core/modules/dblog/tests/src/Functional/DbLogTest.php
index 9f7475b..d2254c7 100644
--- a/core/modules/dblog/tests/src/Functional/DbLogTest.php
+++ b/core/modules/dblog/tests/src/Functional/DbLogTest.php
@@ -136,6 +136,24 @@ public function testLogEventPage() {
   }
 
   /**
+   * Test not-existing log event page.
+   */
+  public function testLogEventNotFoundPage() {
+    // Login the admin user.
+    $this->drupalLogin($this->adminUser);
+
+    // Random (not existing) event ID.
+    $connection = Database::getConnection();
+    $wid = $connection->query('SELECT MAX(wid) FROM {watchdog}')->fetchField();
+    $wid += rand(100, 999);
+
+    // Try to read details of not existing event.
+    $this->drupalGet('admin/reports/dblog/event/' . $wid);
+    // Verify 404 response.
+    $this->assertResponse(404);
+  }
+
+  /**
    * Test individual log event page with missing log attributes.
    *
    * In some cases few log attributes are missing. For example: