diff --git a/src/Lexer.php b/src/Lexer.php
index 9ff028c87..975b0b924 100644
--- a/src/Lexer.php
+++ b/src/Lexer.php
@@ -19,6 +19,8 @@ use Twig\Error\SyntaxError;
  */
 class Lexer
 {
+    private $isInitialized = false;
+
     private $tokens;
     private $code;
     private $cursor;
@@ -61,6 +63,15 @@ class Lexer
             'whitespace_line_chars' => ' \t\0\x0B',
             'interpolation' => ['#{', '}'],
         ], $options);
+    }
+
+    private function initialize()
+    {
+        if ($this->isInitialized) {
+            return;
+        }
+
+        $this->isInitialized = true;
 
         // when PHP 7.3 is the min version, we will be able to remove the '#' part in preg_quote as it's part of the default
         $this->regexes = [
@@ -153,6 +164,8 @@ class Lexer
 
     public function tokenize(Source $source): TokenStream
     {
+        $this->initialize();
+
         $this->source = $source;
         $this->code = str_replace(["\r\n", "\r"], "\n", $source->getCode());
         $this->cursor = 0;