MySQL - Conditional Foreign Key Constraints

I have following comments table in my app:

comments
--------
id           INT
foreign_id   INT
model        TEXT
comment_text TEXT
...

the idea of this table is to store comments for various parts of my app - it can store comments for blog post i.e.:

1|34|blogpost|lorem ipsum...

user picture:

2|12|picture|lorem ipsum...

and so on.

now, is there a way to force FOREIGN KEY constraint on such data?

i.e. something like this in comments table:

FOREIGN KEY (`foreign_id`) REFERENCES blogposts (`id`)
-- but only when model='blogpost'