diff --git a/activesupport/lib/active_support/multibyte/chars.rb b/activesupport/lib/active_support/multibyte/chars.rb
index 3c0cf9f137..4154af8428 100644
--- a/activesupport/lib/active_support/multibyte/chars.rb
+++ b/activesupport/lib/active_support/multibyte/chars.rb
@@ -88,6 +88,12 @@ def split(*args)
# Works like like String#slice!, but returns an instance of
# Chars, or nil if the string was not modified.
+ #
+ # string = 'Welcome'
+ # string.mb_chars.slice!(3) # => #
+ # string # => 'Welome'
+ # string.mb_chars.slice!(0..3) # => #
+ # string # => 'me'
def slice!(*args)
chars(@wrapped_string.slice!(*args))
end