diff --git a/core/designdocument.class.inc.php b/core/designdocument.class.inc.php
index 5c792024a..5268375b0 100644
--- a/core/designdocument.class.inc.php
+++ b/core/designdocument.class.inc.php
@@ -71,7 +71,7 @@ class DesignDocument extends DOMDocument
 		$this->preserveWhiteSpace = true; // otherwise the formatOutput option would have no effect
 	}
 
-	public function loadXML(string $source, int $options = 0)
+	public function loadXML(string $source, int $options = 0) : bool
 	{
 		return parent::loadXML($source, $options | LIBXML_BIGLINES);
 	}