The official way to detect path to Mono runtime is to run pkg-config. The following patch should resolve TODO. Index: Rakefile ==================================================================--- Rakefile (revision 53) +++ Rakefile (working copy) @@ -32,7 +32,8 @@ if ENV[''mono''].nil? FRAMEWORK_DIR = Pathname.new(ENV[''windir''].dup) + ''Microsoft.NET'' + ''Framework'' + ''v2.0.50727'' else - FRAMEWORK_DIR = Pathname.new(''/usr/local/lib/mono/2.0'') # TODO: get mono path from ENV + libdir = IO.popen(''pkg-config --variable=libdir mono'').read.strip + FRAMEWORK_DIR = Pathname.new(libdir) + ''mono'' + ''2.0'' end CS_COMPILER = ENV[''mono''].nil? ? ''csc'' : ''gmcs'' -- Seo Sanghyeon