Strange behavior with Rails find_or_initialize_by_id and Postgresql

The following code sample worked as I would expect when using MySql database - when the :widget_id is 0 it creates a new record with an id of 1; but after switching to Postgresql it was inserting a record into the database with an id of 0 (zero)?

	# this worked as expected on mysql
	# on postgresql it created a new widget with id of 0
	def some_method
	widget = Widget.find_or_initialize_by_id(params[:widget_id])
	# ...
	end
	# workaround code for postgresql
	def some_method
	widget = Widget.find_or_initialize_by_id(params[:widget_id])
	widget = Widget.new if widget.id == 0
	# ...
	end

view raw gistfile1.rb hosted with ❤ by GitHub

Note: params[:widget_id] does have a value of 0 (zero) when I want to generate a new record vs an actual value when doing an edit. This is a non-standard rails form, I did not experience any issues with a standard new/create view/action scenario.