Rails 4+ requires named scopes to be a lambda
and not just a simple Relation
.
Change the old version
scope :active, where(is_active: true)
to the lambda version
scope :active, lambda { where(is_active: true) }
or even shorter to
scope :active, -> { where(is_active: true) }
For more information about named scopes and how to pass parameters, I suggest reading about Scopes in the Rails Guide