diff --git a/includes/class-autoloader.php b/includes/class-autoloader.php
index 73e16ef..e001356 100644
--- a/includes/class-autoloader.php
+++ b/includes/class-autoloader.php
@@ -87,6 +87,9 @@ public function load( $class_name ) {
 			$namespace  = \str_replace( '_', '-', $namespace );
 			$class_name = \substr( $class_name, $last_ns_pos + 1 );
 			$dir        = \str_replace( self::NS_SEPARATOR, DIRECTORY_SEPARATOR, $namespace ) . DIRECTORY_SEPARATOR;
+			if ( $dir ) {
+				$dir = ucfirst( $dir );
+			}
 		}
 
 		$path = $this->path . $dir . 'class-' . \str_replace( '_', '-', $class_name ) . '.php';
diff --git a/readme.md b/readme.md
index 51e59b0..cd0370a 100644
--- a/readme.md
+++ b/readme.md
@@ -5,7 +5,7 @@
 - Tags: webmention, pingback, trackback, linkback, indieweb
 - Requires at least: 6.3
 - Tested up to: 6.8
-- Stable tag: 5.4.0
+- Stable tag: 5.4.1
 - Requires PHP: 7.2
 - License: MIT
 - License URI: https://opensource.org/licenses/MIT
@@ -101,6 +101,10 @@ While not all display options can be settings, we are looking to provide some si
 
 Project and support maintained on github at [pfefferle/wordpress-webmention](https://github.com/pfefferle/wordpress-webmention).
 
+### 5.4.1
+
+* Fix autoloader
+
 ### 5.4.0
 
 * Update yoast/phpunit-polyfills requirement from ^2.0 to ^3.0
diff --git a/webmention.php b/webmention.php
index b006b04..42d9d6f 100755
--- a/webmention.php
+++ b/webmention.php
@@ -5,7 +5,7 @@
  * Description: Webmention support for WordPress posts
  * Author: Matthias Pfefferle
  * Author URI: https://notiz.blog/
- * Version: 5.4.0
+ * Version: 5.4.1
  * License: MIT
  * License URI: https://opensource.org/licenses/MIT
  * Text Domain: webmention
@@ -14,7 +14,7 @@
 
 namespace Webmention;
 
-\define( 'WEBMENTION_VERSION', '5.4.0' );
+\define( 'WEBMENTION_VERSION', '5.4.1' );
 
 \define( 'WEBMENTION_PLUGIN_DIR', \plugin_dir_path( __FILE__ ) );
 \define( 'WEBMENTION_PLUGIN_BASENAME', \plugin_basename( __FILE__ ) );