Permission to execute stored procedure for db-role

I would like to give the role db_datareaderpermission to execute a specific stored procedure.

Is this possible, and if so, how can I achieve this? I tried to add the role on the permissions tab of the stored procedure, but this does not seem to work, the role is not accepted as a valid object.

Edit
Based on a response from cainz, I tried GRANT EXECUTE ON [SP_NAME] TO db_datareader, however the message was:

Msg 4617, Level 16, State 1, Line 1
Cannot grant, deny or revoke permissions to or from special roles.

It seems impossible what I wanted to do.