The API is returning the following error message when I request the revision history for locked posts.

Example URL: http://api.stackoverflow.com/1.1/revisions/194812

{
  "error": {
    "code": 500,
    "message": "A generic error has occurred on the server; developers have been notified."
  }
}

I've tried this through the API Console, directly in my browser, and in code (with and without an API key).

Here's a sample from some of the top posts on Stack Overflow.

Locked:

• List of freely available programming books
• What is the single most influential book every programmer should read?
• Hidden Features of C#?
• Strangest language feature [closed]
• What are the lesser known but cool data structures?

Not locked:

• Hidden features of Python
• Flash CS4 refuses to let go
• What IDE to use for Python?
• What is the name of this operator: “-->”?
• RegEx match open tags except XHTML self-contained tags
• The Definitive C++ Book Guide and List
• Most useful free .NET libraries? [closed]

All of the locked questions give the error message above, while all of the questions that are not locked return a normal revision history. Other question states like closed and protected seem to have no effect.

Finally, I did one last test. I was able to successfully fetch the revision history of Twitter image encoding challenge [closed] before it was locked (note that is was protected and closed prior to testing) but after it was locked I got the same error message.