FieldError: Invalid related_query_name

FieldError: Invalid related_query_name

$ python manage.py makemigrations
...
FieldError: 'related_query_name' must be a valid name

Why this happens

You provided an invalid related_query_name (contains spaces or conflicts with existing fields).

Fix

Use a valid Python identifier and ensure it doesn’t clash with fields or managers.

Wrong code

class Book(models.Model):
    author = models.ForeignKey(Author, on_delete=models.CASCADE, related_query_name="bad name")

Fixed code

class Book(models.Model):
    author = models.ForeignKey(Author, on_delete=models.CASCADE, related_query_name="books")

# Usage
Author.objects.filter(books__title__icontains="Django")