diff --git a/src/colvarproxy.h b/src/colvarproxy.h
index 0268f11b1..387548ad8 100644
--- a/src/colvarproxy.h
+++ b/src/colvarproxy.h
@@ -719,7 +719,7 @@ class colvarproxy
   /// Track which features have been acknowledged during the last run
   size_t features_hash;
 
-private:
+protected:
 
   /// Name of the simulation engine that the derived proxy object supports
   std::string engine_name_ = "standalone";