-

diff --git a/docroot/core/lib/Drupal/Core/Asset/CssCollectionRenderer.php b/docroot/core/lib/Drupal/Core/Asset/CssCollectionRenderer.php
index 869abe3..d17e0f3 100644
--- a/docroot/core/lib/Drupal/Core/Asset/CssCollectionRenderer.php
+++ b/docroot/core/lib/Drupal/Core/Asset/CssCollectionRenderer.php
@@ -80,7 +80,10 @@ class CssCollectionRenderer implements AssetCollectionRendererInterface {
     // browser-caching. The string changes on every update or full cache
     // flush, forcing browsers to load a new copy of the files, as the
     // URL changed.
-    $query_string = $this->state->get('system.css_js_query_string') ?: '0';
+    if (($query_string = $this->state->get('system.css_js_query_string', NULL)) && $query_string === NULL) {
+      $query_string = base_convert(REQUEST_TIME, 10, 36);
+      $this->state->set('system.css_js_query_string', $query_string);
+    }
 
     // Defaults for LINK and STYLE elements.
     $link_element_defaults = array(