diff -u b/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
--- b/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/ConfigImportSubscriber.php
@@ -113,7 +113,12 @@
 
     // Get the active install profile from the site's configuration.
     $current_core_extension = $config_importer->getStorageComparer()->getTargetStorage()->read('core.extension');
-    $install_profile = isset($current_core_extension['profile']) ? $current_core_extension['profile'] : NULL;
+    if (isset($current_core_extension['profile'])) {
+      // Ensure the active profile is not changing.
+      if ($current_core_extension['profile'] !== $core_extension['profile']) {
+        $config_importer->logError($this->t('Cannot change the install profile from %new_profile to %profile once Drupal is installed.', ['%profile' => $install_profile, '%new_profile' => $core_extension['profile']]));
+      }
+    }
 
     // Get a list of installed profiles.
     $installed_profiles = \Drupal::service('profile_handler')->getProfiles();
@@ -144,9 +149,4 @@
       $config_importer->logError($message);
     }
-
-    // Ensure the active profile is not changing.
-    if ($install_profile !== $core_extension['profile']) {
-      $config_importer->logError($this->t('Cannot change the install profile from %new_profile to %profile once Drupal is installed.', ['%profile' => $install_profile, '%new_profile' => $core_extension['profile']]));
-    }
   }