diff --git a/TwigCS/src/Token/Tokenizer.php b/TwigCS/src/Token/Tokenizer.php
index 6631c79..5cd46f9 100644
--- a/TwigCS/src/Token/Tokenizer.php
+++ b/TwigCS/src/Token/Tokenizer.php
@@ -704,7 +704,7 @@ protected function lexPunctuation(): void
                 do {
                     array_pop($this->bracketsAndTernary);
                     $lastBracket = end($this->bracketsAndTernary);
-                } while ('?' === $lastBracket[0]);
+                } while (false !== $lastBracket && '?' === $lastBracket[0]);
 
                 // This is maybe the end of the variable, start again.
                 $this->lexVariable();