diff --git a/vagrant/install-on-travis-ci.sh b/vagrant/install-on-travis-ci.sh
index d7c91f9f..3b8ed190 100755
--- a/vagrant/install-on-travis-ci.sh
+++ b/vagrant/install-on-travis-ci.sh
@@ -64,5 +64,6 @@ tee settings/local.php << EOF
  @define('CONST_Website_BaseURL', '/nominatim/');
  @define('CONST_Database_DSN', 'pgsql:dbname=test_api_nominatim');
  @define('CONST_Wikipedia_Data_Path', CONST_BasePath.'/test/testdb');
+ @define('CONST_Replication_Max_Diff_size', '3');
 EOF