Redmine

I want send html code to a custom_field
With the API I send this Value:
<p>My First Google Map</p>

Result(NOT OK):
<custom_field id="173" name="Imput Parameter" field_format="text" internal_name="">
<value>{"p"=>"My First Google Map"}</value>

Result when I use the Custom Field Editor(OK):
<custom_field id="173" name="Imput Parameter" field_format="text" internal_name="">
<value><p>My First Google Map</p> </value>

Can I change the field_format to code or how to send a html code with the api?