diff --git a/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
index dd6703b..aaa3464 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php
@@ -181,7 +181,7 @@ protected function variable_set($name, $value) {
    */
   protected function refreshVariables() {
     // No operation if the child has not been upgraded yet.
-    if (!$this->upgradedSite) {
+    if ($this->upgradedSite) {
       global $conf;
       cache('bootstrap')->delete('variables');
       $conf = variable_initialize();
@@ -263,6 +263,9 @@ protected function performUpgrade($register_errors = TRUE) {
     // of the child site directly from this request.
     $this->upgradedSite = TRUE;
 
+    // Force a variable refresh as we only just enabled it.
+    $this->refreshVariables();
+
     // Reload module list for modules that are enabled in the test database
     // but not on the test client.
     system_list_reset();