diff --git a/test/ruby/test_rubyoptions.rb b/test/ruby/test_rubyoptions.rb
index 8ea4225139..76be9152a7 100644
--- a/test/ruby/test_rubyoptions.rb
+++ b/test/ruby/test_rubyoptions.rb
@@ -306,7 +306,7 @@ class TestRubyOptions < Test::Unit::TestCase
 
     assert_in_out_err(%w(--parser=prism -e) + ["puts :hi"], "", %w(hi), warning)
     assert_in_out_err(%w(--parser=prism -W:no-experimental -e) + ["puts :hi"], "", %w(hi), [])
-    assert_in_out_err(%w(--parser=prism -W:no-experimental --dump=parsetree -e :hi), "", /"hi"/, [])
+    assert_in_out_err(%w(--parser=prism -W:no-experimental --dump=parsetree -e _=:hi), "", /"hi"/, [])
 
     assert_in_out_err(%w(--parser=parse.y -e) + ["puts :hi"], "", %w(hi), [])
     assert_norun_with_rflag('--parser=parse.y', '--version', "")