sqldiff shows wrong constraint?

class AttachmentManager:
    class Meta:
         constraints = [
            models.UniqueConstraint(
                fields=['workflow'], condition=Q(is_primary=True), name='unique primary attachment')
        ]

ALTER TABLE "workflows_attachmentmanager" ADD CONSTRAINT "workflows_attachmentmanager_workflow_id_c003521f_uniq" UNIQUE ("workflow_id");