Deploying additional files into AWS Lambda (Python)

I am attempting to upload an additional file containing an encryption secret to AWS Lambda, and am having trouble. The file is to be read from my Python script and be processed. I have tested this functionality locally, and it works just fine.

I package and upload the .zip correctly, as AWS has no problems running the script once it uploads. However, my code fails at the line that it reads my file, even though it should be in the working directory.

Is it possible to upload a file into the AWS zip deployment, and have it be read by the script?