diff --git a/src/Logger/DebugFileLogger.php b/src/Logger/DebugFileLogger.php
index edff37f8a..777a24d51 100644
--- a/src/Logger/DebugFileLogger.php
+++ b/src/Logger/DebugFileLogger.php
@@ -38,6 +38,8 @@
 use Infection\Process\MutantProcessInterface;
 
 /**
+ * This file is used for tests only.
+ *
  * @internal
  */
 final class DebugFileLogger extends FileLogger