diff --git a/src/Parser/TokenIterator.php b/src/Parser/TokenIterator.php
index cd5d1b8..841dbe4 100644
--- a/src/Parser/TokenIterator.php
+++ b/src/Parser/TokenIterator.php
@@ -86,7 +86,7 @@ class TokenIterator
 
 		$this->index++;
 
-		if ($this->tokens[$this->index][Lexer::TYPE_OFFSET] === Lexer::TOKEN_HORIZONTAL_WS) {
+		if (($this->tokens[$this->index][Lexer::TYPE_OFFSET] ?? -1) === Lexer::TOKEN_HORIZONTAL_WS) {
 			$this->index++;
 		}
 	}