[Rails Guides] Migrations 3.5 - SQLite Problem

Hello G.s!
I’m in need of your help!

I’m going through this page →

See the code of the example migration at 3.5 - Using the up/down

So I coded everything like this in to my db/migrate folder. Gave it a
version number and all that stuff.
Now when I run “rake db:migrate” it gives me the following error:

rake aborted!
An error has occurred, this and all later migrations canceled:

SQLite3::SQLException: near “CONSTRAINT”: syntax error:
ALTER TABLE products
ADD CONSTRAINT fk_products_categories
FOREIGN KEY (category_id)
REFERENCES categories(id)

Can someone help me with this?