Swapped != for `is not` in a literal string comparison.
@@ -142,7 +142,7 @@ class CrispyFieldNode(template.Node):
# HTML5 required attribute
if html5_required and field.field.required and 'required' not in widget.attrs:
- if field.field.widget.__class__.__name__ is not 'RadioSelect':
+ if field.field.widget.__class__.__name__ != 'RadioSelect':
widget.attrs['required'] = 'required'
for attribute_name, attribute in attr.items():
