diff --git a/d9-upgrade.md b/d9-upgrade.md
index 72dfe7b..03a0ca4 100644
--- a/d9-upgrade.md
+++ b/d9-upgrade.md
@@ -4,7 +4,7 @@
 
 - Make sure the project is using composer 2
 - Make sure the project is using drush 10
-- Make sure the project has at least version ^1.0 of all phpstan related modules (`mglaman/phpstan-drupal`, `phpstan/phpstan-deprecation-rules` and `phpstan/phpstan-phpunit`
+- Make sure the project has at least version ^1.0 of all phpstan related modules (`mglaman/phpstan-drupal`, `phpstan/phpstan-deprecation-rules` `phpstan/extension-installer` and `phpstan/phpstan-phpunit`
 - Make sure the project has upgrade status enabled
 - Make sure the project has `drupal/drupal-extension` version 4 or higher.