How to handle numbers with DynamoDB data import from Amazon S3

I am using the new DynamoDB data import from Amazon S3 functionality and it looks very powerful however my DynamoDB tables are all being generated with strings for every attribute when I am expecting numbers and booleans for some. For example:

my_string,my_number,my_bool
"ABCDEFG",21,true

...ends up as...

{
	"my_string": "ABCDEFG",
	"my_number": "21",
	"my_bool": "true"
}

...when I was expecting...

{
	"my_string": "ABCDEFG",
	"my_number": 21,
	"my_bool": true
}

Is there a way of instructing the import job to encode my attributes correctly?

Many thanks for any advice