diff --git a/core/lib/Drupal/Core/Extension/ModuleInstaller.php b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
index 1f8789d..af7389c 100644
--- a/core/lib/Drupal/Core/Extension/ModuleInstaller.php
+++ b/core/lib/Drupal/Core/Extension/ModuleInstaller.php
@@ -298,12 +298,14 @@ public function install(array $module_list, $enable_dependencies = TRUE) {
 
     // If any modules were newly installed, invoke hook_modules_installed().
     if (!empty($modules_installed)) {
-      // Rebuild routes after installing module. This is done here on top of
-      // \Drupal\Core\Routing\RouteBuilder::destruct to not run into errors on
-      // fastCGI which executes ::destruct() after the module installation page
-      // was sent already.
       \Drupal::getContainer()->set('router.route_provider', \Drupal::service('router.route_provider.old'));
-      \Drupal::service('router.builder')->rebuild();
+      if (!\Drupal::service('router.route_provider.lazy_builder')->hasRebuilt()) {
+        // Rebuild routes after installing module. This is done here on top of
+        // \Drupal\Core\Routing\RouteBuilder::destruct to not run into errors on
+        // fastCGI which executes ::destruct() after the module installation
+        // page was sent already.
+        \Drupal::service('router.builder')->rebuild();
+      }
 
       $this->moduleHandler->invokeAll('modules_installed', array($modules_installed));
     }
diff --git a/core/lib/Drupal/Core/Routing/RouteProviderLazyBuilder.php b/core/lib/Drupal/Core/Routing/RouteProviderLazyBuilder.php
index 6e80ac0..f7ed7d7 100644
--- a/core/lib/Drupal/Core/Routing/RouteProviderLazyBuilder.php
+++ b/core/lib/Drupal/Core/Routing/RouteProviderLazyBuilder.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\Core\Routing\RouteProvider.
+ * Contains \Drupal\Core\Routing\RouteProviderLazyBuilder.
  */
 
 namespace Drupal\Core\Routing;
@@ -16,22 +16,33 @@
 class RouteProviderLazyBuilder implements PreloadableRouteProviderInterface, PagedRouteProviderInterface {
 
   /**
+   * The route provider service.
+   *
    * @var \Drupal\Core\Routing\RouteProviderInterface
    */
   protected $routeProvider;
 
   /**
+   * The route building service.
+   *
    * @var \Drupal\Core\Routing\RouteBuilderInterface
    */
   protected $routeBuilder;
 
   /**
+   * Flag to determine if the router has been rebuilt.
+   *
    * @var bool
    */
   protected $rebuilt = FALSE;
 
   /**
+   * RouteProviderLazyBuilder constructor.
    *
+   * @param \Drupal\Core\Routing\RouteProviderInterface $route_provider
+   *   The route provider service.
+   * @param \Drupal\Core\Routing\RouteBuilderInterface $route_builder
+   *   The route building service.
    */
   public function __construct(RouteProviderInterface $route_provider, RouteBuilderInterface $route_builder) {
     $this->routeProvider = $route_provider;
@@ -39,7 +50,10 @@ public function __construct(RouteProviderInterface $route_provider, RouteBuilder
   }
 
   /**
+   * Gets the real route provider service and rebuilds the router id necessary.
    *
+   * @return \Drupal\Core\Routing\RouteProviderInterface
+   *   The route provider service.
    */
   protected function getRouteProvider() {
     if (!$this->rebuilt) {
@@ -95,7 +109,7 @@ public function getAllRoutes() {
    * {@inheritdoc}
    */
   public function reset() {
-    // Don't call getRouteProvider as this is tricky.
+    // Don't call getRouteProvider as this is results in recursive rebuilds.
     return $this->routeProvider->reset();
   }
 
@@ -113,4 +127,14 @@ public function getRoutesCount() {
     return $this->getRouteProvider()->getRoutesCount();
   }
 
+  /**
+   * Determines if the router has been rebuilt.
+   *
+   * @return bool
+   *   TRUE is the router has been rebuilt, FALSE if not.
+   */
+  public function hasRebuilt() {
+    return $this->rebuilt;
+  }
+
 }