diff -u b/core/lib/Drupal/Core/Config/ConfigFactory.php b/core/lib/Drupal/Core/Config/ConfigFactory.php
--- b/core/lib/Drupal/Core/Config/ConfigFactory.php
+++ b/core/lib/Drupal/Core/Config/ConfigFactory.php
@@ -334,7 +334,8 @@
    */
   public function getCacheKeys($name) {
     return array_filter(array_keys($this->cache), function($key) use ($name) {
-      return preg_match('/^' . preg_quote($name) . ':/', $key);
+      // Return TRUE if the key starts with the configuration name.
+      return strpos($key, $name) === 0;
     });
   }