diff --git a/stdlib/builtin/encoding.rbs b/stdlib/builtin/encoding.rbs
index 3e1c1aa30..98ba5be74 100644
--- a/stdlib/builtin/encoding.rbs
+++ b/stdlib/builtin/encoding.rbs
@@ -173,6 +173,8 @@ Encoding::Big5_HKSCS_2008: Encoding
 
 Encoding::Big5_UAO: Encoding
 
+Encoding::CESU_8: Encoding
+
 Encoding::CP1250: Encoding
 
 Encoding::CP1251: Encoding