diff --git a/activesupport/lib/active_support/core_ext/file/atomic.rb b/activesupport/lib/active_support/core_ext/file/atomic.rb
index 976d462e8e5ff..8cc5654a4bf38 100644
--- a/activesupport/lib/active_support/core_ext/file/atomic.rb
+++ b/activesupport/lib/active_support/core_ext/file/atomic.rb
@@ -27,7 +27,7 @@ def atomic_write(file_name, temp_dir = Dir.tmpdir)
             old_stat = stat(file_name)
           rescue Errno::ENOENT
             # No old permissions, write a temp file to determine the defaults
-            check_name = ".permissions_check.#{Thread.current.object_id}.#{Process.pid}.#{rand(1000000)}"
+            check_name = join(dirname(file_name), ".permissions_check.#{Thread.current.object_id}.#{Process.pid}.#{rand(1000000)}")
             open(check_name, "w") { }
             old_stat = stat(check_name)
             unlink(check_name)