What version are you running? 1.5.4 What's the URL of the page containing the problem? http://example.com/r/4976/diff/ What steps will reproduce the problem? 1. Create a non-trivial (more than a few dozen lines) C++ source file with two newlines after the last function definition (revision 1) 2. Change the above file to add or remove newlines to the end of the file 3. Post a diff covering the change from step 2 to reviewboard 4. Attempt to view the diff (View Diff link) What is the expected output? What do you see instead? Expected: the diff viewer Actual: IndexError in get_interesting_headers, where it accesses 'lines' What operating system are you using? What browser? Ubuntu. Any browser. Please provide any additional information below. I fixed the problem locally by wrapping 'if is_modified_file: / ... / else: / ...' with 'try: / ... / except IndexError: / raise StopIteration'. (Sorry, I don't have a clean diff against 1.5.4 to post) Based on the surrounding code and method names, the code in question is trying to get a context function name. If your diff is trivial (only this file), the whole view-diff page refuses to load. If the diff is non-trivial, the asynchronous diff fetching will only fail for files with that type of change--however, it will prevent viewing any diff chunks for that file.