diff --git a/extensions/openpower-pels/generic.hpp b/extensions/openpower-pels/generic.hpp
index 892e249..ff85b03 100644
--- a/extensions/openpower-pels/generic.hpp
+++ b/extensions/openpower-pels/generic.hpp
@@ -40,7 +40,7 @@
      *
      * @param[in] stream - The stream to write to
      */
-    void flatten(Stream& stream) override;
+    void flatten(Stream& stream) const override;
 
     /**
      * @brief Returns the size of this section when flattened into a PEL