diff --git a/src/ModelDescriber/Annotations/SymfonyConstraintAnnotationReader.php b/src/ModelDescriber/Annotations/SymfonyConstraintAnnotationReader.php
index db69a41b6..49a923cc3 100644
--- a/src/ModelDescriber/Annotations/SymfonyConstraintAnnotationReader.php
+++ b/src/ModelDescriber/Annotations/SymfonyConstraintAnnotationReader.php
@@ -213,7 +213,7 @@ private function getAnnotations(Context $parentContext, $reflection, ?array $val
      */
     private function locateAnnotations($reflection): \Traversable
     {
-        if (\PHP_VERSION_ID >= 80000) {
+        if (\PHP_VERSION_ID >= 80000 && class_exists(Constraint::class)) {
             foreach ($reflection->getAttributes(Constraint::class, \ReflectionAttribute::IS_INSTANCEOF) as $attribute) {
                 yield $attribute->newInstance();
             }