diff --git a/pkgs/development/interpreters/ruby/build-ruby-gem/gem-post-build.rb b/pkgs/development/interpreters/ruby/build-ruby-gem/gem-post-build.rb
index 112a9accc33..4480c525bf1 100644
--- a/pkgs/development/interpreters/ruby/build-ruby-gem/gem-post-build.rb
+++ b/pkgs/development/interpreters/ruby/build-ruby-gem/gem-post-build.rb
@@ -64,8 +64,7 @@ spec.executables.each do |exe|
 # this file is here to facilitate running it.
 #
 
-gem_path = ENV["GEM_PATH"]
-ENV["GEM_PATH"] = "\#{gem_path}\#{":" unless gem_path.nil? || gem_path.empty?}#{(gem_path+[gem_home]).join(":")}"
+Gem.use_paths "#{gem_home}", #{gem_path.to_s}
 
 require 'rubygems'