diff --git a/src/MDFormatter.php b/src/MDFormatter.php
index 736c236..1f0c324 100644
--- a/src/MDFormatter.php
+++ b/src/MDFormatter.php
@@ -77,6 +77,19 @@ final class MDFormatter {
 
     }
 
+    /**
+     * Applies markdown formatting for fourth level headline.
+     *
+     * @param string $input Headline text.
+     *
+     * @return string
+     */
+    public static function formatMarkdownHeadline4(string $input):string {
+
+        return '#### ' . $input . PHP_EOL;
+
+    }
+
     /**
      * Returns a horizontal rule in markdown.
      *