Prawn error with image cells

prawn_error_image_cells.rb

@pdf = Prawn::Document.new(:margin=>0)
image = "#{Prawn::BASEDIR}/data/images/prawn.png"
@imgcell = Prawn::Table::Cell.make(@pdf, :image=>image)



ArgumentError: Content type not recognized: nil
	from /Users/rzolkos/.rvm/gems/ruby-1.9.2-p180/gems/prawn-0.12.0/lib/prawn/table/cell.rb:127:in `make'
	from (irb):6
	from /Users/rzolkos/.rvm/rubies/ruby-1.9.2-p180/bin/irb:16:in `<main>'

The prawn.png image goes exist. In IRB, the 2nd line returns the full path to the prawn.png file. As it should.

This error occured due to using v0.12 of the gem instead of master. Master has support for images inside table cells.