diff --git a/core/lib/Drupal/Core/Template/TwigEnvironment.php b/core/lib/Drupal/Core/Template/TwigEnvironment.php
index 6b21282..f0a8050 100644
--- a/core/lib/Drupal/Core/Template/TwigEnvironment.php
+++ b/core/lib/Drupal/Core/Template/TwigEnvironment.php
@@ -214,7 +214,11 @@ public function getTemplateClass($name, $index = NULL, $inline = FALSE) {
    * Warning: You should use the render element 'twig_inline' together with
    * the #template attribute instead of this method directly.
    * On top of that you have to ensure that the template string is not dynamic
-   * but just an ordinary static php string.
+   * but just an ordinary static php string, because there may be installations
+   * using read-only PHPStorage that want to generate all possible twig
+   * templates as part of a build step. So it is important that an automated
+   * script can find the templates and extract them. This is only possible if
+   * the template is a regular string.
    *
    * @param string $template_string
    *   The template string to render with placeholders.