--- a/vendor/magento/framework/View/Asset/PreProcessor/FileNameResolver.php
+++ b/vendor/magento/framework/View/Asset/PreProcessor/FileNameResolver.php
@@ -40,6 +40,7 @@
      */
     public function resolve($fileName)
     {
+        $fileName = (string)$fileName;
         $compiledFile = $fileName;
         $extension = pathinfo($fileName, PATHINFO_EXTENSION);
         foreach ($this->alternativeSources as $name => $alternative) {