diff --git a/test/ruby/test_rubyoptions.rb b/test/ruby/test_rubyoptions.rb
index 15271cd6e8..6e501a45b6 100644
--- a/test/ruby/test_rubyoptions.rb
+++ b/test/ruby/test_rubyoptions.rb
@@ -116,7 +116,7 @@ class TestRubyOptions < Test::Unit::TestCase
   def test_verbose
     assert_in_out_err(["-vve", ""]) do |r, e|
       assert_match(VERSION_PATTERN, r[0])
-      if RbConfig::CONFIG['cppflags'].match?(/(\A|\s)-DMJIT_FORCE_ENABLE\b/)
+      if RbConfig::CONFIG.fetch('cppflags', '').match?(/(\A|\s)-DMJIT_FORCE_ENABLE\b/)
         assert_equal(RUBY_DESCRIPTION, r[0])
       else
         assert_equal(NO_JIT_DESCRIPTION, r[0])