Need (2) posts in Chained Dropdown

Hello every one.
I implemented Victor’s solution ( How to Implement Dependent/Chained Dropdown List with Django ) in my project. All works fine except that after selecting the city and submiting the form an error required field appears for city field. Nonetheless, after returning and keeping the same region, selecting again the same city ando submitting it again then it is accepted.

I wonder if any of you have an idea of what is going on there,

Best regards

Well, I just found the bug. It was located in the tiny html where I had in the option {{ city_id }} instead of {{ city.pk }}.

Victor, This is a great Post. THANKS !!!