diff --git a/test/plugin/test_output_as_buffered_backup.rb b/test/plugin/test_output_as_buffered_backup.rb
index 2e27c9aca7..0a65ad681e 100644
--- a/test/plugin/test_output_as_buffered_backup.rb
+++ b/test/plugin/test_output_as_buffered_backup.rb
@@ -173,6 +173,8 @@ def wait_flush(target_file)
       waiting(5) {
         target_dir = File.join(File.dirname(target_file), "*")
         while Dir.glob(target_dir).size.zero?
+          # Avoid to lose globbed entries on Windows in busy loop
+          sleep 0.1 if Fluent.windows?
         end
       }
     end