diff --git a/src/web/twig/Extension.php b/src/web/twig/Extension.php
index 2ad388c33c..057ef4a723 100644
--- a/src/web/twig/Extension.php
+++ b/src/web/twig/Extension.php
@@ -1628,17 +1628,12 @@ class Extension extends AbstractExtension implements GlobalsInterface
      */
     private function _checkFilterSupport($arrow): void
     {
-        if (is_string($arrow)) {
-            $forbidden = ['system', 'passthru', 'exec'];
-
-            $arrow = strtolower($arrow);
-            if (isset($arrow[0]) && $arrow[0] === "\\") {
-                $arrow = substr($arrow, 1);
-            }
-
-            if (in_array($arrow, $forbidden, true)) {
-                throw new RuntimeError('Not supported in this filter.');
-            }
+        if (is_string($arrow) && in_array(ltrim(strtolower($arrow), '\\'), [
+            'system',
+            'passthru',
+            'exec',
+        ])) {
+            throw new RuntimeError('Not supported in this filter.');
         }
     }