Cloudformation external parameter file do not support YAML file

I used aws-cli to update my stacks, and want to use an external yaml file (dev.yaml) as parameters file like below:
```sh
aws cloudformation update-stack --stack-name test --template-body file://./api-test.yaml --parameters file://./dev.yaml
```
In `dev.yaml`, it only has:
```yaml

---
- ParameterKey: APICacheClusterSize
ParameterValue: '1.6'
```
However, I got this Error message when I run the update command above:
```
Error parsing parameter '--parameters': Expected: '=', received: '-' for input:

---
- ParameterKey: APICacheClusterSize
^
ParameterValue: '1.6'
```

If I use JSON file with same context as below, and use it instead of `dev.yaml`, it works fine:
```json
[
{
"ParameterKey": "APICacheClusterSize",
"ParameterValue": "1.6"
}
]
```

So, can the external parameters file for aws cloudformation be YAML file? or will...?