diff --git a/extensions/openpower-pels/private_header.hpp b/extensions/openpower-pels/private_header.hpp
index 7d6a53d..1302182 100644
--- a/extensions/openpower-pels/private_header.hpp
+++ b/extensions/openpower-pels/private_header.hpp
@@ -70,7 +70,7 @@
      *
      * @param[in] stream - The stream to write to
      */
-    void flatten(Stream& stream) override;
+    void flatten(Stream& stream) const override;
 
     /**
      * @brief Returns the creation timestamp
@@ -170,7 +170,7 @@
      *
      * @return CreatorVersion& - the creator version
      */
-    CreatorVersion& creatorVersion()
+    const CreatorVersion& creatorVersion() const
     {
         return _creatorVersion;
     }
@@ -300,7 +300,7 @@
  * @param[out] s - the stream
  * @param[in] cv - the CreatorVersion object
  */
-Stream& operator<<(Stream& s, CreatorVersion& cv);
+Stream& operator<<(Stream& s, const CreatorVersion& cv);
 
 } // namespace pels
 } // namespace openpower