diff --git a/MD_STD.php b/MD_STD.php
index 5cd1c2a..53d48b9 100644
--- a/MD_STD.php
+++ b/MD_STD.php
@@ -8,7 +8,7 @@ declare(strict_types = 1);
  * Standard class providing overrides of default PHP functions as static
  * functions.
  */
-class MD_STD {
+final class MD_STD {
 
     /**
      * Wrapper around file_get_contents, that provides catches errors on it and returns
diff --git a/MD_STD_IN.php b/MD_STD_IN.php
index 2ff0456..9816e5e 100644
--- a/MD_STD_IN.php
+++ b/MD_STD_IN.php
@@ -8,7 +8,7 @@ declare(strict_types = 1);
  * Standard class providing overrides of default PHP functions as static
  * functions.
  */
-class MD_STD_IN {
+final class MD_STD_IN {
 
     /**
      * Validates and sanitizes input integers to be in line with MySQL