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dash.exceptions.IncorrectTypeException when URL Routing

I have been attempting to create a multi-page app using the simple tutorial URL Routing and Multiple Apps and have run into an issue. I copied the code for, but no matter what I do I get an IncorrectTypeException when attempting to run it.

“raise exceptions.IncorrectTypeException(
dash.exceptions.IncorrectTypeException: The input argument url.pathname must be a list or tuple of

My code is:

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output

from app import app
from apps import history_vis_app

app.layout = html.Div([
    dcc.Location(id='url', refresh=False),

@app.callback(Output('page-content', 'children'),Input('url', 'pathname'))
def display_page(pathname):
    if pathname == '/main':
        return history_vis_app.layout
    elif pathname == '/apps/history_vis':
        return history_vis_app.layout
        return '404 dude'

if __name__ == '__main__':

Hi @NoahSyn and welcom to the Dash community! :slight_smile:

Try upgrading to the latest version of Dash