Configure.gem image_science doesn't work


I have an app that requires 6 gems at the moment. config.gem works
fine for most of them, but not for image_science.

ImageScience is installed correctly, and the code works fine. But if I
have the line:

config.gem “image_science”

in my environment.rb, server (and rake tasks, etc.) all quit with the

Missing these required gems:

image_science is installed correctly, in the same directory as all the
other gems, and that directory (/Library/Ruby/Gems/1.8) is correctly
listed among the directories output by the error message:

You’re running:
ruby at /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby
rubygems 1.3.1 at /Users/evan/.gem/ruby/1.8, /Library/Ruby/Gems/1.8, /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8

… So I’m at a loss. Why does config.gem think this particular gem is
not installed?