diff --git a/core/lib/Drupal/Core/Template/TwigPhpStorageCache.php b/core/lib/Drupal/Core/Template/TwigPhpStorageCache.php
index 90572c4..3a524bd 100644
--- a/core/lib/Drupal/Core/Template/TwigPhpStorageCache.php
+++ b/core/lib/Drupal/Core/Template/TwigPhpStorageCache.php
@@ -68,9 +68,6 @@ protected function storage() {
    * {@inheritdoc}
    */
   public function generateKey($name, $className) {
-    // This substring keeps 132 bits of the hash.
-    $hash = substr(Crypt::hashBase64($className), 0, 22);
-
     if (strpos($name, '{# inline_template_start #}') === 0) {
       // $name is an inline template, and can have characters that are not valid
       // for a filename. $hash is unique for each inline template so we just use
@@ -80,21 +77,19 @@ public function generateKey($name, $className) {
     else {
       $name = basename($name);
     }
-    // If the suffix is longer that 45 characters then we truncate it so the
+
+    // If the suffix is longer that 61 characters then we truncate it so the
     // length of the filename can't grow beyond that. Windows only supports 255
     // characters in a path. If the files directory is in the usual place of
     // 'sites/default/files' then the maximum relative path of a twig file is
-    // 153 characters. This is made up of:
+    // 153 characters. We use 148 of that as follows:
     // - 30 (/sites/default/files/php/twig/)
     // - 9 (prefix + _)
-    // - 45 (suffix)
-    // - 69 (/ + hmac_hash + .php)
-    if (strlen($name) > 22) {
-      $name = substr($name, 0, 22);
-    }
-    $suffix = $name . '_' . $hash;
+    // - 61 (suffix)
+    // - 48 (/ + hmac_hash + .php)
+    $suffix = substr($name, 0, 30) . '_' . substr(Crypt::hashBase64($className), 0, 30);
 
-    // The first part is what is invalidated.
+    // The cache prefix is what gets invalidated.
     return $this->templateCacheFilenamePrefix . '_' . $suffix;
   }
 
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index 6dc2663..4568b2a 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -1794,3 +1794,12 @@ function system_update_8203() {
     ->set('logging', 1)
     ->save(TRUE);
 }
+
+/**
+ * Clear caches due to change in Twig template cache names.
+ *
+ * @see \Drupal\Core\Template\TwigPhpStorageCache::generateKey()
+ */
+function system_update_8204() {
+  // Empty update to cause a cache rebuild.
+}
diff --git a/core/tests/Drupal/KernelTests/Core/Theme/TwigEnvironmentTest.php b/core/tests/Drupal/KernelTests/Core/Theme/TwigEnvironmentTest.php
index 06f5826..e9811b4 100644
--- a/core/tests/Drupal/KernelTests/Core/Theme/TwigEnvironmentTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Theme/TwigEnvironmentTest.php
@@ -88,7 +88,7 @@ public function testInlineTemplate() {
 
     $cache = $environment->getCache();
     $class = $environment->getTemplateClass($name);
-    $expected = $hash . '_inline-template_' . substr(Crypt::hashBase64($class), 0, 22);
+    $expected = $hash . '_inline-template_' . substr(Crypt::hashBase64($class), 0, 30);
     $this->assertEqual($expected, $cache->generateKey($name, $class));
   }
 
@@ -117,6 +117,14 @@ public function testCacheFilename() {
     // static cache.
     $environment = \Drupal::service('twig');
 
+    // A template basename > 30 characters should be truncated in the cache key.
+    $cache = $environment->getCache();
+    $long_name = 'core/modules/system/templates/block--system-messages-block.html.twig';
+    $this->assertGreaterThan(30, strlen(basename($long_name)));
+    $class = $environment->getTemplateClass($long_name);
+    $key = $cache->generateKey($long_name, $class);
+    $this->assertEquals(70, strlen($key));
+
     $original_filename = $environment->getCacheFilename('core/modules/system/templates/container.html.twig');
     \Drupal::getContainer()->set('twig', NULL);