diff --git a/core/lib/Drupal/Component/PhpStorage/MTimeProtectedFastFileStorage.php b/core/lib/Drupal/Component/PhpStorage/MTimeProtectedFastFileStorage.php
index f82b676..0a907cf 100644
--- a/core/lib/Drupal/Component/PhpStorage/MTimeProtectedFastFileStorage.php
+++ b/core/lib/Drupal/Component/PhpStorage/MTimeProtectedFastFileStorage.php
@@ -116,6 +116,10 @@ public function save($name, $data) {
    * modified, invalidating the file, thus protecting against untrusted code
    * getting executed.
    *
+   * In an effort to keep paths from getting overly long, we only use the
+   * first 10 hexadecimal characters (2^40 bits). This gives us more than a
+   * trillion unique filenames so unexpected collisions are not an issue.
+   *
    * @param string $name
    *   The virtual file name. Can be a relative path.
    * @param string $directory
@@ -135,7 +139,8 @@ public function getFullPath($name, &$directory = NULL, &$directory_mtime = NULL)
     if (!isset($directory_mtime)) {
       $directory_mtime = file_exists($directory) ? filemtime($directory) : 0;
     }
-    return $directory . '/' . hash_hmac('sha256', $name, $this->secret . $directory_mtime) . '.php';
+    $hashed_name = substr(hash_hmac('sha256', $name, $this->secret . $directory_mtime), 0, 10) . '.php';
+    return $directory . '/' . $hashed_name;
   }
 
   /**
@@ -207,7 +212,10 @@ protected function getContainingDirectoryFullPath($name) {
     if (substr($name, -4) === '.php') {
       $name = substr($name, 0, -4);
     }
-    return $this->directory . '/' . str_replace('/', '#', $name);
+
+    // Prevent overly-long paths when using verbose template suggestions, for
+    // example, by truncating the Twig template name to 30 characters.
+    return $this->directory . '/' . str_replace('/', '#', substr($name, 0, 30));
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Template/TwigPhpStorageCache.php b/core/lib/Drupal/Core/Template/TwigPhpStorageCache.php
index d2cf918..3455e14 100644
--- a/core/lib/Drupal/Core/Template/TwigPhpStorageCache.php
+++ b/core/lib/Drupal/Core/Template/TwigPhpStorageCache.php
@@ -72,7 +72,9 @@ protected function storage() {
    * {@inheritdoc}
    */
   public function generateKey($name, $className) {
-    $hash = hash('sha256', $className);
+    // Prevent overly-long path names by using the first 10 chars of the hash.
+    // This gives us over a trillion potential keys.
+    $hash = substr(hash('sha256', $className), 0, 10);
 
     if (strpos($name, '{# inline_template_start #}') === 0) {
       // $name is an inline template, and can have characters that are not valid