Flask Interactive Debugger Broken

Flask Interactive Debugger Broken

I'm trying to figure out why the Flask interactive debugger isn't working.
My template application is barebones, with a single error:
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
print missing_variable #Error
return 'Hello World!'
if __name__ == '__main__':
app.run(host='0.0.0.0.', debug=True)
But the debugger catches the error, but gives me a non-interactive page
and complains about a lack of Javascript:
The debugger caught an exception in your WSGI application. You can now
look at the traceback which led to the error. If you enable JavaScript you
can also use additional features such as code execution (if the evalex
feature is enabled), automatic pasting of the exceptions and much more.
I haven't disabled Javascript, so I'm not sure why this the interactive
debugger is broken. Thanks!