diff --git a/activesupport/lib/active_support/core_ext/string/multibyte.rb b/activesupport/lib/active_support/core_ext/string/multibyte.rb
index 38224ea5da887bc0a3de762a0e6177763268fbc7..075b206d0451d511973c43f87beb99cd13c71dbd 100644
--- a/activesupport/lib/active_support/core_ext/string/multibyte.rb
+++ b/activesupport/lib/active_support/core_ext/string/multibyte.rb
@@ -12,7 +12,7 @@ class String
   # class. If the proxy class doesn't respond to a certain method, it's forwarded to the encapsulated string.
   #
   #   >> "lj".upcase
-  #   => "lj"
+  #   => "LJ"
   #   >> "lj".mb_chars.upcase.to_s
   #   => "LJ"
   #