diff --git a/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit.php b/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit.php
index 581e26dc3f..cef6c98c29 100644
--- a/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit.php
+++ b/src/Symfony/Bridge/PhpUnit/bin/simple-phpunit.php
@@ -95,19 +95,19 @@ $passthruOrFail = function ($command) {
 
 if (\PHP_VERSION_ID >= 80000) {
     // PHP 8 requires PHPUnit 9.3+
-    $PHPUNIT_VERSION = $getEnvVar('SYMFONY_PHPUNIT_VERSION', '9.4');
+    $PHPUNIT_VERSION = $getEnvVar('SYMFONY_PHPUNIT_VERSION', '9.4') ?: '9.4';
 } elseif (\PHP_VERSION_ID >= 70200) {
     // PHPUnit 8 requires PHP 7.2+
-    $PHPUNIT_VERSION = $getEnvVar('SYMFONY_PHPUNIT_VERSION', '8.3');
+    $PHPUNIT_VERSION = $getEnvVar('SYMFONY_PHPUNIT_VERSION', '8.3') ?: '8.3';
 } elseif (\PHP_VERSION_ID >= 70100) {
     // PHPUnit 7 requires PHP 7.1+
-    $PHPUNIT_VERSION = $getEnvVar('SYMFONY_PHPUNIT_VERSION', '7.5');
+    $PHPUNIT_VERSION = $getEnvVar('SYMFONY_PHPUNIT_VERSION', '7.5') ?: '7.5';
 } elseif (\PHP_VERSION_ID >= 70000) {
     // PHPUnit 6 requires PHP 7.0+
-    $PHPUNIT_VERSION = $getEnvVar('SYMFONY_PHPUNIT_VERSION', '6.5');
+    $PHPUNIT_VERSION = $getEnvVar('SYMFONY_PHPUNIT_VERSION', '6.5') ?: '6.5';
 } elseif (\PHP_VERSION_ID >= 50600) {
     // PHPUnit 4 does not support PHP 7
-    $PHPUNIT_VERSION = $getEnvVar('SYMFONY_PHPUNIT_VERSION', '5.7');
+    $PHPUNIT_VERSION = $getEnvVar('SYMFONY_PHPUNIT_VERSION', '5.7') ?: '5.7';
 } else {
     // PHPUnit 5.1 requires PHP 5.6+
     $PHPUNIT_VERSION = '4.8';