diff --git a/lang/en/validation.php b/lang/en/validation.php
index 5ea01fa7..ac8ddb0a 100644
--- a/lang/en/validation.php
+++ b/lang/en/validation.php
@@ -71,6 +71,7 @@
     'ipv4' => 'The :attribute must be a valid IPv4 address.',
     'ipv6' => 'The :attribute must be a valid IPv6 address.',
     'json' => 'The :attribute must be a valid JSON string.',
+    'lowercase' => 'The :attribute must be lowercase.',
     'lt' => [
         'array' => 'The :attribute must have less than :value items.',
         'file' => 'The :attribute must be less than :value kilobytes.',