--- a/rspec-support/spec/rspec/support/spec/shell_out_spec.rb
+++ b/rspec-support/spec/rspec/support/spec/shell_out_spec.rb
@@ -4,17 +4,17 @@ RSpec.describe RSpec::Support::ShellOut,
   include described_class
 
   it 'shells out and returns stdout and stderr' do
-    stdout, stderr, _ = shell_out("ruby", "-e", "$stdout.print 'yes'; $stderr.print 'no'")
+    stdout, stderr, _ = shell_out(RbConfig::ruby, "-e", "$stdout.print 'yes'; $stderr.print 'no'")
     expect(stdout).to eq("yes")
     expect(stderr).to eq("no")
   end
 
   it 'returns the exit status as the third argument' do
-    _, _, good_status = shell_out("ruby", "-e", '3 + 3')
+    _, _, good_status = shell_out(RbConfig::ruby, "-e", '3 + 3')
     expect(good_status.exitstatus).to eq(0)
 
     unless RUBY_VERSION.to_f < 1.9 # except 1.8...
-      _, _, bad_status = shell_out("ruby", "-e", 'boom')
+      _, _, bad_status = shell_out(RbConfig::ruby, "-e", 'boom')
       expect(bad_status.exitstatus).to eq(1)
     end
   end