diff --git a/src/Neon/Parser.php b/src/Neon/Parser.php
index f53eca1..a2a4a1c 100644
--- a/src/Neon/Parser.php
+++ b/src/Neon/Parser.php
@@ -240,7 +240,7 @@ private function checkArrayKey(Node $key, array &$arr): void
 	}
 
 
-	private function injectPos(Node $node, int $start = null, int $end = null): Node
+	private function injectPos(Node $node, ?int $start = null, ?int $end = null): Node
 	{
 		$node->startTokenPos = $start ?? $this->tokens->getPos();
 		$node->startLine = $this->posToLine[$node->startTokenPos];