diff --git a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
index eb7c5a3..da2ba82 100644
--- a/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
@@ -857,7 +857,11 @@ abstract class WebTestBase extends TestBase {
     file_unmanaged_delete_recursive($this->originalFileDirectory . '/simpletest/' . substr($this->databasePrefix, 10));
 
     // Remove all prefixed tables.
-    $tables = db_find_tables($this->databasePrefix . '%');
+    $connection_info = Database::getConnectionInfo('default');
+    $tables = db_find_tables($connection_info[$target]['prefix']['default'] . '%');
+    if (empty($tables)) {
+      $this->fail('Failed to find test tables to drop.');
+    }
     foreach ($tables as $table) {
       if (db_drop_table(substr($table, strlen($this->databasePrefix)))) {
         unset($tables[$table]);