diff --git a/core/scripts/run-tests.sh b/core/scripts/run-tests.sh
index 3754ebdf393cab9eba3ad3f8e532d45ba09ed57d..ae489e1c772ec43b2932e0f9ca6de09d31316290 100755
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -33,12 +33,12 @@
 
 // Bootstrap to perform initial validation or other operations.
 drupal_bootstrap(DRUPAL_BOOTSTRAP_CODE);
-simpletest_classloader_register();
 
 if (!\Drupal::moduleHandler()->moduleExists('simpletest')) {
-  simpletest_script_print_error("The simpletest module must be enabled before this script can run.");
+  simpletest_script_print_error("The Testing (simpletest) module must be installed before this script can run.");
   exit;
 }
+simpletest_classloader_register();
 
 if ($args['clean']) {
   // Clean up left-over times and directories.