Problem while export to xls using spreadsheet gem in rails for Server

Hi All,

In my code

@format_text = @workbook.add_format(:bold =>false)

I get following error

undefined method `font' for {:bold =>false}:Hash in

when i try to export data into the XLS i am using following gems

spreadsheet --version 0.6.4
spreadsheet-excel --version

My problem is when i use same code with same gems it works fine on my
local application but same gives error on my heroku server