diff --git a/modules/simpletest/simpletest.module b/modules/simpletest/simpletest.module
index 717474912f703ee1e369a47469ee4a070fbcd580..e1bf2c45f534c0b0a578de2ea8f341a2f68ba4d9 100644
--- a/modules/simpletest/simpletest.module
+++ b/modules/simpletest/simpletest.module
@@ -195,6 +195,7 @@ function _simpletest_batch_finished($success, $results, $operations, $elapsed) {
     simpletest_log_read($operations[0][1][1]);
 
     drupal_set_message(t('The test run did not successfully finish.'), 'error');
+    drupal_set_message(t('Please use the <em>Clean environment</em> button to clean-up temporary files and tables.'), 'warning');
   }
   module_invoke_all('test_group_finished');
 }