diff --git a/core/modules/system/src/Tests/Cache/ChainedFastBackendUnitTest.php b/core/modules/system/src/Tests/Cache/ChainedFastBackendUnitTest.php
index c34563c..1c484fa 100644
--- a/core/modules/system/src/Tests/Cache/ChainedFastBackendUnitTest.php
+++ b/core/modules/system/src/Tests/Cache/ChainedFastBackendUnitTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\system\Tests\Cache;
 
+use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\Cache\ChainedFastBackend;
 use Drupal\Core\Cache\DatabaseBackend;
 use Drupal\Core\Cache\PhpBackend;
@@ -34,4 +35,31 @@ protected function createCacheBackend($bin) {
     return $backend;
   }
 
+  /**
+   * Test permanent TTL.
+   */
+  function testPermanentTtl() {
+    $bin = 'test';
+    $consistent_backend = new DatabaseBackend(\Drupal::service('database'), \Drupal::service('cache_tags.invalidator.checksum'), $bin);
+    $consistent_backend->setPermanentTtl(2);
+    $fast_backend = new DatabaseBackend(\Drupal::service('database'), \Drupal::service('cache_tags.invalidator.checksum'), $bin);
+    $consistent_backend->setPermanentTtl(4);
+    $backend = new ChainedFastBackend($consistent_backend, $fast_backend, $bin);
+    $cid = 'test';
+    $value = 'test';
+    $backend->set($cid, $value);
+
+    // The item expiry will be taken from the fast backend, so reflects the
+    // settings on that backend.
+    $item = $backend->get($cid);
+    $this->assertTrue($item->expire !== CacheBackendInterface::CACHE_PERMANENT);
+    $this->assertTrue($item->expire <= REQUEST_TIME + 4 * DatabaseBackend::JITTER_MULTIPLIER);
+    $item = $consistent_backend->get($cid);
+    $this->assertTrue($item->expire !== CacheBackendInterface::CACHE_PERMANENT);
+    $this->assertTrue($item->expire <= REQUEST_TIME + 4 * DatabaseBackend::JITTER_MULTIPLIER);
+    $item = $fast_backend->get($cid);
+    $this->assertTrue($item->expire !== CacheBackendInterface::CACHE_PERMANENT);
+    $this->assertTrue($item->expire <= REQUEST_TIME + 2 * DatabaseBackend::JITTER_MULTIPLIER);
+  }
+
 }