diff --git a/bin/add-phpstan-self-replace.php b/bin/add-phpstan-self-replace.php
new file mode 100644
index 00000000000..e65922b0427
--- /dev/null
+++ b/bin/add-phpstan-self-replace.php
@@ -0,0 +1,20 @@
+<?php
+
+// this is part of downgrade build
+
+declare(strict_types=1);
+
+use Nette\Utils\FileSystem;
+use Nette\Utils\Json;
+
+require __DIR__ . '/../vendor/autoload.php';
+
+$composerJsonFileContents = FileSystem::read(__DIR__ . '/../composer.json');
+
+$composerJson = Json::decode($composerJsonFileContents, Json::FORCE_ARRAY);
+$composerJson['replace']['phpstan/phpstan'] = $composerJson['require']['phpstan/phpstan'];
+
+$modifiedComposerJsonFileContents = Json::encode($composerJson, Json::PRETTY);
+FileSystem::write(__DIR__ . '/../composer.json', $modifiedComposerJsonFileContents);
+
+echo 'Done!' . PHP_EOL;
diff --git a/build/build-rector-scoped.sh b/build/build-rector-scoped.sh
index 7ceab8d6e12..deeba59917c 100644
--- a/build/build-rector-scoped.sh
+++ b/build/build-rector-scoped.sh
@@ -36,6 +36,9 @@ wget https://github.com/humbug/php-scoper/releases/download/0.17.7/php-scoper.ph
 # Work around possible PHP memory limits
 php -d memory_limit=-1 php-scoper.phar add-prefix bin config src packages rules vendor composer.json --output-dir "../$RESULT_DIRECTORY" --config scoper.php --force --ansi --working-dir "$BUILD_DIRECTORY";
 
+php bin/add-phpstan-self-replace.php
+composer remove phpstan/phpstan -W
+
 note "Dumping Composer Autoload"
 composer dump-autoload --working-dir "$RESULT_DIRECTORY" --ansi --classmap-authoritative --no-dev