1 files changed, 10 insertions, 8 deletions
diff --git a/guides/source/active_record_migrations.md b/guides/source/active_record_migrations.md
index a45becf670..d91c9bd606 100644
--- a/guides/source/active_record_migrations.md
+++ b/guides/source/active_record_migrations.md
@@ -467,6 +467,8 @@ the first time (i.e. on the date the migration is applied).
 Some adapters may support additional options; see the adapter specific API docs
 for further information.
 
+NOTE: `null` and `default` cannot be specified via command line.
+
 ### Foreign Keys
 
 While it's not required you might want to add foreign key constraints to
@@ -1018,10 +1020,10 @@ such features, the `execute` method can be used to execute arbitrary SQL.
 Migrations and Seed Data
 ------------------------
 
-The main purpose of Rails' migration feature is to issue commands that modify the 
-schema using a consistent process. Migrations can also be used 
-to add or modify data. This is useful in an existing database that can't be destroyed 
-and recreated, such as a production database. 
+The main purpose of Rails' migration feature is to issue commands that modify the
+schema using a consistent process. Migrations can also be used
+to add or modify data. This is useful in an existing database that can't be destroyed
+and recreated, such as a production database.
 
 ```ruby
 class AddInitialProducts < ActiveRecord::Migration[5.0]
@@ -1037,10 +1039,10 @@ class AddInitialProducts < ActiveRecord::Migration[5.0]
 end
 ```
 
-To add initial data after a database is created, Rails has a built-in 
-'seeds' feature that makes the process quick and easy. This is especially 
-useful when reloading the database frequently in development and test environments. 
-It's easy to get started with this feature: just fill up `db/seeds.rb` with some 
+To add initial data after a database is created, Rails has a built-in
+'seeds' feature that makes the process quick and easy. This is especially
+useful when reloading the database frequently in development and test environments.
+It's easy to get started with this feature: just fill up `db/seeds.rb` with some
 Ruby code, and run `rails db:seed`:
 
 ```ruby