diff --git a/README.md b/README.md
index 2f1ddbe..a7aa1e4 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@ Laravel Mail CSS Inliner
 Most email clients won't render CSS (on a `<link>` or a `<style>`). The solution is inline your CSS directly on the HTML. Doing this by hand easily turns into unmantainable templates.
 The goal of this package is to automate the process of inlining that CSS before sending the emails.
 
-## Installation and compatability
+## Installation and compatibility
 
 Starting with version 5 this package requires PHP 8.0 and Laravel 9.0 or higher.
 
diff --git a/src/CssInlinerPlugin.php b/src/CssInlinerPlugin.php
index ee2ff17..cb15dc4 100644
--- a/src/CssInlinerPlugin.php
+++ b/src/CssInlinerPlugin.php
@@ -19,7 +19,7 @@ class CssInlinerPlugin
 
     private string $cssToAlwaysInclude;
 
-    public function __construct(array $filesToInline = [], CssToInlineStyles $converter = null)
+    public function __construct(array $filesToInline = [], ?CssToInlineStyles $converter = null)
     {
         $this->cssToAlwaysInclude = $this->loadCssFromFiles($filesToInline);