This problem can be illustrated by using the attached tar file, or the Github repo at https://github.com/keithrbennett/underscore_file_test. When Ruby version == 2.4.1 and current directory is the project root of this project and the gem is built and installed and the executable is run from the gem without preceding it with 'ruby' and the executable is run without specifying a directory (i.e. as 'underscore_file_test', not 'bin/underscore_file_test') Then (FILE below should be FILE surrounded by double underscores) ```ruby __FILE__ => $PROJECT_ROOT/exe/underscore_file_test ``` instead of pointing to a directory in the GEM_PATH, something like: ```ruby __FILE__ => /Users/kbennett/.rvm/gems/ruby-2.4.1/bin/underscore_file_test ``` This error occurred with Ruby 2.4.1 but not: * ruby 2.0.0p648 (2015-12-16 revision 53162) [x86_64-darwin15.6.0] * ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin16] * ruby 2.4.0p0 (2016-12-24 revision 57164) [x86_64-darwin16] * jruby 184.108.40.206 (2.3.1) 2017-01-11 68056ae Java HotSpot(TM) 64-Bit Server VM 25.77-b03 on 1.8.0_77-b03 +jit [darwin-x86_64] My development machine was a MacBookPro running MacOs Sierra. `uname -a` output is: * Darwin MacBook-Pro-KB-13.local 16.7.0 Darwin Kernel Version 16.7.0: Wed Oct 4 00:17:00 PDT 2017; root:xnu-3789.71.6~1/RELEASE_X86_64 x86_64 ## Steps to Reproduce: * Download or git clone the Github project tree, or the attached tarball. * Change directory to the project root. * Run: `clear; gem build *gemspec && gem install *gem && underscore_file_test` * Note the directory component of the output. If you cd somewhere else, the output will be correct, i.e. will be located in a GEM_PATH directory. If you run the command from the project root using a different Ruby, it may work. I have not tested this on versions _later than_ 2.4.1.