diff --git a/core/lib/Drupal/Core/Routing/RouteBuilder.php b/core/lib/Drupal/Core/Routing/RouteBuilder.php
index c3809db..e9692c5 100644
--- a/core/lib/Drupal/Core/Routing/RouteBuilder.php
+++ b/core/lib/Drupal/Core/Routing/RouteBuilder.php
@@ -121,22 +121,6 @@ public function __construct(MatcherDumperInterface $dumper, LockBackendInterface
   }
 
   /**
-   * Refreshes the local cache and rechecks if a rebuild is needed.
-   *
-   * @return bool
-   *   TRUE if the rebuild is needed, FALSE otherwise.
-   */
-  protected function isRebuildNeededUncached() {
-    // To absolutely ensure that the router rebuild is required, reset the cache
-    // in case they were set by another process.
-    $this->routeBuilderIndicator->resetCache();
-    if ($this->routeBuilderIndicator->isRebuildNeeded()) {
-      return TRUE;
-    }
-    return FALSE;
-  }
-
-  /**
    * {@inheritdoc}
    */
   public function rebuild() {
@@ -150,7 +134,7 @@ public function rebuild() {
       // available, resulting in a 404.
       $this->lock->wait('router_rebuild');
 
-      if ($this->isRebuildNeededUncached()) {
+      if ($this->routeBuilderIndicator->isRebuildStillNeeded()) {
         $this->rebuild();
       }
 
@@ -236,7 +220,7 @@ public function getCollectionDuringRebuild() {
    */
   public function rebuildIfNeeded() {
     if ($this->routeBuilderIndicator->isRebuildNeeded()) {
-      if (!$this->isRebuildNeededUncached()) {
+      if (!$this->routeBuilderIndicator->isRebuildStillNeeded()) {
         return FALSE;
       }
       return $this->rebuild();
diff --git a/core/lib/Drupal/Core/Routing/RouteBuilderIndicator.php b/core/lib/Drupal/Core/Routing/RouteBuilderIndicator.php
index 5cff225..3496ddd 100644
--- a/core/lib/Drupal/Core/Routing/RouteBuilderIndicator.php
+++ b/core/lib/Drupal/Core/Routing/RouteBuilderIndicator.php
@@ -59,4 +59,14 @@ public function setRebuildDone() {
     $this->state->set(static::REBUILD_NEEDED, FALSE);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function isRebuildStillNeeded() {
+    // To absolutely ensure that the router rebuild is required, reset the cache
+    // in case they were set by another process.
+    $this->resetCache();
+    return $this->isRebuildNeeded();
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Routing/RouteBuilderIndicatorInterface.php b/core/lib/Drupal/Core/Routing/RouteBuilderIndicatorInterface.php
index da9f97b..7838acb 100644
--- a/core/lib/Drupal/Core/Routing/RouteBuilderIndicatorInterface.php
+++ b/core/lib/Drupal/Core/Routing/RouteBuilderIndicatorInterface.php
@@ -41,4 +41,16 @@ public function setRebuildDone();
    */
   public function isRebuildNeeded();
 
+  /**
+   * Checks if the router rebuild really needed.
+   *
+   * This method should not rely on any static caching.
+   *
+   * This method is called during route rebuilding if acquiring a lock failed.
+   *
+   * @return bool
+   *   TRUE if the router still needs to be rebuilt, FALSE if not.
+   */
+  public function isRebuildStillNeeded();
+
 }
diff --git a/core/tests/Drupal/Tests/Core/Routing/RouteBuilderTest.php b/core/tests/Drupal/Tests/Core/Routing/RouteBuilderTest.php
index 5e50083..d25cc58 100644
--- a/core/tests/Drupal/Tests/Core/Routing/RouteBuilderTest.php
+++ b/core/tests/Drupal/Tests/Core/Routing/RouteBuilderTest.php
@@ -282,6 +282,10 @@ public function testRebuildIfNecessary() {
                 ->method('isRebuildNeeded')
                 ->will($this->onConsecutiveCalls(TRUE, TRUE, FALSE));
 
+    $this->routeBuilderIndicator->expects($this->exactly(2))
+      ->method('isRebuildStillNeeded')
+      ->will($this->onConsecutiveCalls(TRUE, FALSE));
+
     $this->yamlDiscovery->expects($this->any())
                         ->method('findAll')
                         ->will($this->returnValue(array()));
@@ -293,6 +297,9 @@ public function testRebuildIfNecessary() {
 
     // This will not trigger a rebuild.
     $this->assertFalse($this->routeBuilder->rebuildIfNeeded());
+
+    // This will not trigger a rebuild, because the indicator is not set at all.
+    $this->assertFalse($this->routeBuilder->rebuildIfNeeded());
   }
 }