CloudFormation won't update CloudFrontDistribution DNS

I used this cloud formation stack 1.5 years ago, and both create/update worked fine. Now I'm finding I receiving an error.

I created my stack with...
aws cloudformation create-stack --template-body file://./blog.yml \
--region us-east-1 \
--stack-name ${stack_name} --parameters \
ParameterKey=DomainName,ParameterValue=${domain_name}

stack_name=blog-test-mydomain-org
domain_name=blog-test.mydomain.org

That worked just fine. Then I tried to update

aws cloudformation update-stack --template-body file://./blog.yml \
--region us-east-1 \
--stack-name blog-test-mydomain-org

And received...
One or more of the CNAMEs you provided are already associated with a different resource. (Service: AmazonCloudFront; Status Code: 409; Error Code: CNAMEAlreadyExists; Request ID: c5865945-1bff-410e-b33a-44332038fac6; Proxy: null)

I can't believe that cloudformation would try and create another CNAME when it's already in use by that stack. That's just weird. Any ideas here? Like I say, it worked 1.5 years ago and simply doesn't work now.