diff --git a/lib/puma/const.rb b/lib/puma/const.rb
index bb85eefdd0..3aa9374ba0 100644
--- a/lib/puma/const.rb
+++ b/lib/puma/const.rb
@@ -53,6 +53,7 @@ class UnsupportedOption < RuntimeError
     415 => 'Unsupported Media Type',
     416 => 'Range Not Satisfiable',
     417 => 'Expectation Failed',
+    418 => 'I\'m A Teapot',
     422 => 'Unprocessable Entity',
     423 => 'Locked',
     424 => 'Failed Dependency',