diff --git a/build/rector-downgrade-vendor.php b/build/rector-downgrade-vendor.php
index ac772345385..454dba02274 100644
--- a/build/rector-downgrade-vendor.php
+++ b/build/rector-downgrade-vendor.php
@@ -16,6 +16,8 @@
 	$targetPhpVersionId = $parsePhpVersion($targetPhpVersion);
 
 	$parameters = $containerConfigurator->parameters();
+	$parameters->set(Option::PARALLEL, true);
+
 	$parameters->set(Option::PHP_VERSION_FEATURES, $targetPhpVersionId);
 
 	$services = $containerConfigurator->services();
diff --git a/build/rector-downgrade.php b/build/rector-downgrade.php
index 76224ef58e6..07baddbfd0a 100644
--- a/build/rector-downgrade.php
+++ b/build/rector-downgrade.php
@@ -23,6 +23,7 @@
 	$targetPhpVersionId = $parsePhpVersion($targetPhpVersion);
 
 	$parameters = $containerConfigurator->parameters();
+	$parameters->set(Option::PARALLEL, true);
 
 	$parameters->set(Option::PHP_VERSION_FEATURES, $targetPhpVersionId);
 	$parameters->set(Option::SKIP, [