diff --git a/test/irb/test_completion.rb b/test/irb/test_completion.rb
index de043c7088..04ac6dba5b 100644
--- a/test/irb/test_completion.rb
+++ b/test/irb/test_completion.rb
@@ -64,7 +64,9 @@ module TestIRB
     end
 
     def test_complete_require_relative
-      candidates = IRB::InputCompletor::CompletionProc.("'lib/irb", "require_relative ", "")
+      candidates = Dir.chdir(__dir__ + "/../..") do
+        IRB::InputCompletor::CompletionProc.("'lib/irb", "require_relative ", "")
+      end
       %w['lib/irb/init 'lib/irb/ruby-lex].each do |word|
         assert_include candidates, word
       end