diff --git a/tapeserver/castor/tape/tapeserver/daemon/DataTransferSessionTest.cpp b/tapeserver/castor/tape/tapeserver/daemon/DataTransferSessionTest.cpp
index 937da7a2f5c76456667395342810fd7d3fad749f..1c12d10465f24aa029b5eb37fc3341d81a0548ca 100644
--- a/tapeserver/castor/tape/tapeserver/daemon/DataTransferSessionTest.cpp
+++ b/tapeserver/castor/tape/tapeserver/daemon/DataTransferSessionTest.cpp
@@ -132,6 +132,13 @@ protected:
     }
   }
 
+  /**
+   * Temporary directory created with mkdtemp that will be used to contain the
+   * destination remote files of the tests that need to create them.
+   *
+   * Please note that a new temporary directory is created and deleted for each
+   * test by the Setup() and TearDown() methods.
+   */
   char m_tmpDir[100];
 
   class MockArchiveJob: public cta::ArchiveJob {