diff --git a/.github/workflows/phpunit-bridge.yml b/.github/workflows/phpunit-bridge.yml
new file mode 100644
index 0000000000000..bdda65de1b6f5
--- /dev/null
+++ b/.github/workflows/phpunit-bridge.yml
@@ -0,0 +1,28 @@
+name: PhpUnitBridge
+
+on:
+    push:
+        paths:
+            - 'src/Symfony/Bridge/PhpUnit/**'
+    pull_request:
+        paths:
+            - 'src/Symfony/Bridge/PhpUnit/**'
+
+jobs:
+
+    lint:
+        name: Lint
+        runs-on: ubuntu-latest
+
+        steps:
+            -   name: Checkout
+                uses: actions/checkout@v2
+
+            -   name: Setup PHP
+                uses: shivammathur/setup-php@v2
+                with:
+                    coverage: "none"
+                    php-version: "5.5"
+
+            -   name: Lint
+                run: find ./src/Symfony/Bridge/PhpUnit -name '*.php' | grep -v -e /Tests/ -e ForV6 -e ForV7 -e ForV8 -e ForV9 -e ConstraintLogicTrait | parallel -j 4 php -l {}
diff --git a/src/Symfony/Bridge/PhpUnit/ClassExistsMock.php b/src/Symfony/Bridge/PhpUnit/ClassExistsMock.php
index e8ca4ac9402a8..d61d7887be891 100644
--- a/src/Symfony/Bridge/PhpUnit/ClassExistsMock.php
+++ b/src/Symfony/Bridge/PhpUnit/ClassExistsMock.php
@@ -30,17 +30,23 @@ public static function withMockedClasses(array $classes)
 
     public static function class_exists($name, $autoload = true)
     {
-        return (bool) (self::$classes[ltrim($name, '\\')] ?? \class_exists($name, $autoload));
+        $name = ltrim($name, '\\');
+
+        return isset(self::$classes[$name]) ? (bool) self::$classes[$name] : \class_exists($name, $autoload);
     }
 
     public static function interface_exists($name, $autoload = true)
     {
-        return (bool) (self::$classes[ltrim($name, '\\')] ?? \interface_exists($name, $autoload));
+        $name = ltrim($name, '\\');
+
+        return isset(self::$classes[$name]) ? (bool) self::$classes[$name] : \interface_exists($name, $autoload);
     }
 
     public static function trait_exists($name, $autoload = true)
     {
-        return (bool) (self::$classes[ltrim($name, '\\')] ?? \trait_exists($name, $autoload));
+        $name = ltrim($name, '\\');
+
+        return isset(self::$classes[$name]) ? (bool) self::$classes[$name] : \trait_exists($name, $autoload);
     }
 
     public static function register($class)