diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index 3d4d2aea2e61894914fba39fc6b0b69c121e9309..e3b5d22721f4e8f6403ee4dc1dac6a2e23cda5d3 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Document the :message option for validates_associated. Closes #10357 [dylans]
+
 * Document automatically generated predicate methods for attributes. Closes #10373 [chuyeow]
 
 * Added ActiveRecord::Base#becomes to turn a record into one of another class (mostly relevant for STIs) [DHH]. Example:
diff --git a/activerecord/lib/active_record/validations.rb b/activerecord/lib/active_record/validations.rb
index 0ee8f84c6254529b577be2ffae29c15a2556fe76..3b8ffe4e0607cacf147b28d070864bf3d22341de 100755
--- a/activerecord/lib/active_record/validations.rb
+++ b/activerecord/lib/active_record/validations.rb
@@ -777,6 +777,7 @@ def validates_exclusion_of(*attr_names)
       # is both present and guaranteed to be valid, you also need to use validates_presence_of.
       #
       # Configuration options:
+      # * <tt>message</tt> - A custom error message (default is: "is invalid")
       # * <tt>on</tt> Specifies when this validation is active (default is :save, other options :create, :update)
       # * <tt>if</tt> - Specifies a method, proc or string to call to determine if the validation should
       #   occur (e.g. :if => :allow_validation, or :if => Proc.new { |user| user.signup_step > 2 }).  The