diff --git a/test/irb/test_raise_no_backtrace_exception.rb b/test/irb/test_raise_no_backtrace_exception.rb
index d4ca50a85..3031f000e 100644
--- a/test/irb/test_raise_no_backtrace_exception.rb
+++ b/test/irb/test_raise_no_backtrace_exception.rb
@@ -29,7 +29,7 @@ def test_raise_exception_with_different_encoding_containing_invalid_byte_sequenc
         ENV["HOME"] = tmpdir
 
         bundle_exec = ENV.key?('BUNDLE_GEMFILE') ? ['-rbundler/setup'] : []
-        File.open('euc.rb', 'w') do |f|
+        File.open("#{tmpdir}/euc.rb", 'w') do |f|
           f.write(<<~EOF)
             # encoding: euc-jp
 
@@ -38,7 +38,11 @@ def raise_euc_with_invalid_byte_sequence
             end
           EOF
         end
-        assert_in_out_err(bundle_exec + %w[-rirb -W0 -e ENV[%(LC_ALL)]=%(ja_JP.UTF-8) -e ENV[%(LANG)]=%(ja_JP.UTF-8) -e IRB.start(__FILE__) -- -f --], <<~IRB, /`raise_euc_with_invalid_byte_sequence': あ\\xFF \(RuntimeError\)/, [], encoding: "UTF-8")
+        env = {}
+        %w(LC_MESSAGES LC_ALL LC_CTYPE LANG).each {|n| env[n] = "ja_JP.UTF-8" }
+        args = [env] + bundle_exec + %W[-rirb -C #{tmpdir} -W0 -e IRB.start(__FILE__) -- -f --]
+        error = /`raise_euc_with_invalid_byte_sequence': あ\\xFF \(RuntimeError\)/
+        assert_in_out_err(args, <<~IRB, error, [], encoding: "UTF-8")
           require_relative 'euc'
           raise_euc_with_invalid_byte_sequence
         IRB