diff --git a/activesupport/test/core_ext/file_test.rb b/activesupport/test/core_ext/file_test.rb
index 0c32858809..b9d4c11d80 100644
--- a/activesupport/test/core_ext/file_test.rb
+++ b/activesupport/test/core_ext/file_test.rb
@@ -85,7 +85,7 @@ class AtomicWriteTest < ActiveSupport::TestCase
 
   private
     def file_name
-      "atomic.file"
+      "atomic-#{Process.pid}.file"
     end
 
     def file_mode