User guide's multipage demo breaks

I was having some strange errors trying to make a multipage dashboard, so I replicated the demo app at the bottom of the multipage documentation page.

However, running gave me an error:

Traceback (most recent call last):
  File "", line 6, in <module>
    from apps import app1, app2
  File "XXXXX/app/apps/", line 24, in <module>
    [Input('app-1-dropdown', 'value')])
  File "XXXXX/anaconda3/lib/python3.6/site-packages/dash/dash.p", line 485, in callback
    self._validate_callback(output, inputs, state, events)
  File "XXXXX/anaconda3/lib/python3.6/site-packages/dash/", line 471, in _validate_callback
    output.component_property).replace('    ', ''))
You have already assigned a callback to the output
with ID "app-1-display-value" and property "children". An output can only have
a single callback function. Try combining your inputs and
callback functions together into one function.

For the life of me, I can’t backtrace the solution. Any help appreciated.

Nevermind, as always in the act of posting I figured out the issue. needed to have its values changed from “app-1” etc to “app-2”