DeploymentBucket with serverSideEncryption using kms

I’m trying to do use a previously created DeploymentBucket (encrypted with my own kms key)
So I have
deploymentBucket:
name: myBucket
serverSideEncryption: aws:kms
SSEKMSKeyId: arn:aws:kms:eu-west-1:123hashkey456etc
but I get ServerlessError: Access Denied …. (aws/provider/awsProvider.js:316:27)

Is KMS encryption supported?
Docs only mentioned AES256