diff --git a/.github/workflows/phpstan.yml b/.github/workflows/phpstan.yml
index c70ea7ed6..3e20e5aa3 100644
--- a/.github/workflows/phpstan.yml
+++ b/.github/workflows/phpstan.yml
@@ -50,6 +50,7 @@ jobs:
         run: "composer config platform --unset && composer update ${{ env.COMPOSER_FLAGS }}"
 
       - name: Run PHPStan
+        # Locked to phpunit 7.5 here as newer ones have void return types which break inheritance
         run: |
-          bin/composer require --dev phpstan/phpstan:^0.12.42 phpunit/phpunit:^9.3 --with-all-dependencies
+          bin/composer require --dev phpstan/phpstan:^0.12.42 phpunit/phpunit:^7.5.20 --with-all-dependencies
           vendor/bin/phpstan analyse --configuration=phpstan/config.neon
diff --git a/phpstan/config.neon b/phpstan/config.neon
index c5d67ffeb..c08b7833a 100644
--- a/phpstan/config.neon
+++ b/phpstan/config.neon
@@ -26,6 +26,7 @@ parameters:
 
         # BC with older PHPUnit
         - '~^Call to an undefined static method Composer\\Test\\PolyfillTestCase::setExpectedException\(\)\.$~'
+        - '~^Call to an undefined method Composer\\Test\\[a-zA-Z0-9\\]+::(assertFileDoesNotExist|assertMatchesRegularExpression)\(\)\.$~'
 
     paths:
         - ../src