acm.Certificate is having issues getting values for ValidationDomain (e.g. '9]}') with imported values

[ghost]

This code:
import acm = require('@aws-cdk/aws-certificatemanager');
import cdk = require('@aws-cdk/core');

export class ExampleStack extends cdk.Stack {
constructor(app: cdk.App, id: string) {
super(app, id);

 const certificate = new acm.Certificate(this, 'Certificate', {
  domainName: "application-dns." + cdk.Fn.importValue('Route53ZoneDomain'),
  validationMethod: acm.ValidationMethod.EMAIL,
})

certificate.certificateArn

}
}

const app = new cdk.App();
new ExampleStack(app, 'ExampleApp');
app.synth();

Reproduction Steps

Running the above produces the following resource definition:

Resources:
Certificate4E7ABB08:
Type: AWS::CertificateManager::Certificate
Properties:
DomainName:
Fn::Join:
- ""
- - application-dns.
- Fn::ImportValue: Route53ZoneDomain-rc0
DomainValidationOptions:
- DomainName:
Fn::Join:
- ""
- - application-dns.
- Fn::ImportValue: Route53ZoneDomain-rc0
ValidationDomain: 9]}
ValidationMethod: EMAIL
Metadata:
aws:cdk:path: ExampleStack/Certificate/Resource
CDKMetadata:
Type: AWS::CDK::Metadata
Properties:
Modules: aws-cdk=1.9.0,@aws-cdk/assets=1.9.0,@aws-cdk/aws-certificatemanager=1.9.0,@aws-cdk/aws-cloudformation=1.9.0,@aws-cdk/aws-cloudwatch=1.9.0,@aws-cdk/aws-ec2=1.9.0,@aws-cdk/aws-events=1.9.0,@aws-cdk/aws-iam=1.9.0,@aws-cdk/aws-kms=1.9.0,@aws-cdk/aws-lambda=1.9.0,@aws-cdk/aws-s3=1.9.0,@aws-cdk/aws-s3-assets=1.9.0,@aws-cdk/aws-sqs=1.9.0,@aws-cdk/aws-ssm=1.9.0,@aws-cdk/core=1.9.0,@aws-cdk/cx-api=1.9.0,@aws-cdk/region-info=1.9.0,jsii-runtime=node.js/v12.4.0

Bolded is the issue.

If I replace the import value with a string it all works as expected.

Resources:
Certificate4E7ABB08:
Type: AWS::CertificateManager::Certificate
Properties:
DomainName: application-dns.dev.example.com
DomainValidationOptions:
- DomainName: application-dns.dev.example.com
ValidationDomain: example.com
ValidationMethod: EMAIL
Metadata:
aws:cdk:path: ExampleStack/Certificate/Resource
CDKMetadata:
Type: AWS::CDK::Metadata
Properties:
Modules: aws-cdk=1.9.0,@aws-cdk/assets=1.9.0,@aws-cdk/aws-certificatemanager=1.9.0,@aws-cdk/aws-cloudformation=1.9.0,@aws-cdk/aws-cloudwatch=1.9.0,@aws-cdk/aws-ec2=1.9.0,@aws-cdk/aws-events=1.9.0,@aws-cdk/aws-iam=1.9.0,@aws-cdk/aws-kms=1.9.0,@aws-cdk/aws-lambda=1.9.0,@aws-cdk/aws-s3=1.9.0,@aws-cdk/aws-s3-assets=1.9.0,@aws-cdk/aws-sqs=1.9.0,@aws-cdk/aws-ssm=1.9.0,@aws-cdk/core=1.9.0,@aws-cdk/cx-api=1.9.0,@aws-cdk/region-info=1.9.0,jsii-runtime=node.js/v12.4.0
Condition: CDKMetadataAvailable

Error Log

Environment

• CLI Version :
• Framework Version: 1.9.0
• OS MacOS :
• Language :Typescript

Other

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