Invalid instance_type while creating Amazon RDS db.r3 instance from Ansible playbook

I'm trying to create an Amazon RDS instance using Ansible RDS module and getting the following error when instance_type is db.r3.large.

msg: value of instance_type must be one of: db.t1.micro,db.m1.small,db.m1.medium,db.m1.large,db.m1.xlarge,db.m2.xlarge,db.m2.2xlarge,db.m2.4xlarge,db.m3.medium,db.m3.large,db.m3.xlarge,db.m3.2xlarge,db.cr1.8xlarge, got: db.r3.large

However, db.r3.large is a valid type as described here and I can create one manually from AWS console (i.e. without Ansible playbook).

Here is my vars file:

instance_name: my-instance-name
region: us-east-1
zone: us-east-1b
size: 100
instance_type: db.r3.large
db_engine: MySQL
engine_version: 5.6.21
subnet: my-subnet
parameter_group: default.mysql5.6
security_groups: my-security-group
db_name: my-db-name
db_username: root
db_password: my-password

And here is my playbook:

---
- name: Playbook to provision RDS instance
  hosts: localhost
  connection: local
  gather_facts: no

  vars_files:
    - vars/rds.yml

  tasks:
    - name: Create MySQL RDS Instance
      local_action:
        module: rds
        command: create
        instance_name: "{{ instance_name }}"
        region: "{{ region }}"
        zone: "{{ zone }}"
        size: "{{ size }}"
        instance_type: "{{ instance_type }}"
        db_engine: "{{ db_engine }}"
        engine_version: "{{ engine_version }}"
        subnet: "{{ subnet }}"
        parameter_group: "{{ parameter_group }}"
        multi_zone: no
        db_name: "{{ db_name }}"
        username: "{{ db_username }}"
        password: "{{ db_password }}"
        vpc_security_groups: "{{ security_groups }}"
        maint_window: Sun:04:00-Sun:08:00
        backup_retention: 30
        backup_window: 01:00-3:00

subnet, vpc_security_groups, region, zone etc. are fine as I'm able to create db.r3.large instance with same settings from the AWS console.

It seems that something is wrong with Ansible module or boto, but I could not find out anything helpful. My ansible version is 1.6.1, boto version is 2.36.0 and botocore version is 0.94.0.

How can I create db.r3.large instance form Ansible?