[Answered ]-ModelForm with overrides throwing ValueError

The documentation of ChoiceField states:

• Empty value: '' (an empty string)
• Normalizes to: A Unicode object.

In fact, invalid literal for int() with base 10: ” is the result of calling int on an empty string.

What you want to use is a TypedChoiceField:

• Empty value: Whatever you’ve given as empty_value
• Normalizes to: A value of the type provided by the coerce argument.

In your case, you should use TypedChoiceField the same way you were using ChoiceField, except that you should also add the empty_value=0 parameter.