diff --git a/required.php b/required.php
index b9493e7..065f1ba 100644
--- a/required.php
+++ b/required.php
@@ -150,6 +150,7 @@ function lang($key, $echo = true) {
     if (array_key_exists($key, STRINGS)) {
         $str = STRINGS[$key];
     } else {
+        trigger_error("Language key \"$key\" does not exist in " . LANGUAGE, E_USER_WARNING);
         $str = $key;
     }
 
@@ -172,6 +173,7 @@ function lang2($key, $replace, $echo = true) {
     if (array_key_exists($key, STRINGS)) {
         $str = STRINGS[$key];
     } else {
+        trigger_error("Language key \"$key\" does not exist in " . LANGUAGE, E_USER_WARNING);
         $str = $key;
     }