grunt-aws-s3: Missing required key 'Key' in params

Im getting a missing key ‘key’ error when attempting to upload to s3. In the AWS SDK release notes it mentions this as a validation error. https://aws.amazon.com/releasenotes/JavaScript/6967335344676381

The Error

MissingRequiredParameter: Missing required key 'Key' in params

My Config

          stage: {
            options: {
              bucket: 'my_s3_bucket',
              differential: true,
              params: {
                key: '',
                CacheControl: '3000'
              }
            },
            files: [
              {src: ['dist/**'], cwd: '', action: 'upload'},
            ]
          },