diff --git a/src/ExpressionParser.php b/src/ExpressionParser.php
index f4690babd..bb4d5e2a0 100644
--- a/src/ExpressionParser.php
+++ b/src/ExpressionParser.php
@@ -196,10 +196,7 @@ class ExpressionParser
                     $class = $this->unaryOperators[$token->getValue()]['class'];
 
                     $ref = new \ReflectionClass($class);
-                    if (!(\in_array($ref->getName(), [NegUnary::class, PosUnary::class, 'Twig_Node_Expression_Unary_Neg', 'Twig_Node_Expression_Unary_Pos'])
-                        || $ref->isSubclassOf(NegUnary::class) || $ref->isSubclassOf(PosUnary::class)
-                        || $ref->isSubclassOf('Twig_Node_Expression_Unary_Neg') || $ref->isSubclassOf('Twig_Node_Expression_Unary_Pos'))
-                    ) {
+                    if (!\in_array($class, [NegUnary::class, PosUnary::class])) {
                         throw new SyntaxError(sprintf('Unexpected unary operator "%s".', $token->getValue()), $token->getLine(), $this->parser->getStream()->getSourceContext());
                     }