diff -u b/core/modules/system/src/Form/ModulesUninstallConfirmForm.php b/core/modules/system/src/Form/ModulesUninstallConfirmForm.php
--- b/core/modules/system/src/Form/ModulesUninstallConfirmForm.php
+++ b/core/modules/system/src/Form/ModulesUninstallConfirmForm.php
@@ -136,7 +136,7 @@
     // Prevent this page from showing when the module list is empty.
     if (empty($this->modules)) {
       drupal_set_message($this->t('The selected modules could not be uninstalled, either due to a website problem or due to the uninstall confirmation form timing out. Please try again.'), 'error');
-      return new RedirectResponse($this->getCancelUrl()->toString());
+      return new RedirectResponse($this->getCancelUrl()->setOption('absolute', TRUE)->toString());
     }
 
     $data = system_rebuild_module_data();