ruby - mini_magick initialize error wrong number of arguments (0 for 1) -

i'm experiencing strange behaviour minimagick

everything works fine on every develop workations in production this:

wrong number of arguments (0 1) 

if execute

service nginx restart 

i get

imagemagick/graphicsmagick not installed 

only 1 time. every future reload of page arguments error.

here's code

require 'rubygems' require 'sinatra/base' require 'mini_magick'  '/test'       minimagick::image.open("/webapps/myapp/testimg.png")   end 

if execute convert:

# convert -version version: imagemagick 6.9.0-10 q16 x86_64 2015-03-20 http://www.imagemagick.org copyright: copyright (c) 1999-2015 imagemagick studio llc license: http://www.imagemagick.org/script/license.php features: dpc openmp delegates (built-in): xml zlib 

any idea?