diff --git a/src/Extension/SandboxExtension.php b/src/Extension/SandboxExtension.php
index 7705ffb688a..2230810359f 100644
--- a/src/Extension/SandboxExtension.php
+++ b/src/Extension/SandboxExtension.php
@@ -63,11 +63,12 @@ public function isSandboxedGlobally()
         return $this->sandboxedGlobally;
     }
 
-    private function isSourceSandboxed(?Source $source) : bool
+    private function isSourceSandboxed(?Source $source): bool
     {
-        if ($source === null || $this->sourcePolicy === null) {
+        if (null === $source || null === $this->sourcePolicy) {
             return false;
         }
+
         return $this->sourcePolicy->enableSandbox($source);
     }