fix

Author: staabm

src/XMLSerializer.php

@@ -34,13 +34,14 @@ public function toXML(TokenCollection $tokens): string {
         $writer->openMemory();
         $writer->setIndent(true);
 
+        $writer->startDocument();
         $this->appendToWriter($writer, $tokens);
+        $writer->endDocument();
 
         return $writer->outputMemory();
     }
 
     public function appendToWriter(XMLWriter $writer, TokenCollection $tokens): void {
-        $writer->startDocument();
         $writer->startElement('source');
         $writer->writeAttribute('xmlns', $this->xmlns->asString());
 
@@ -75,6 +76,5 @@ public function appendToWriter(XMLWriter $writer, TokenCollection $tokens): void
         }
 
         $writer->endElement();
-        $writer->endDocument();
     }
 }