diff --git a/include/GModelSpatialComposite.hpp b/include/GModelSpatialComposite.hpp
index a79ba5b..a00516a 100644
--- a/include/GModelSpatialComposite.hpp
+++ b/include/GModelSpatialComposite.hpp
@@ -79,7 +79,7 @@ public:
     int                  components(void) const;
     void                 append(const GModelSpatial& component,
                                 const std::string&   name = "",
-                                double scale = 1.);
+                                const double& scale = 1.);
     const GModelSpatial* component(const int& index) const;
     const GModelSpatial* component(const std::string& name) const;
     double               component_scale(const int& index) const;
diff --git a/src/model/GModelSpatialComposite.cpp b/src/model/GModelSpatialComposite.cpp
index 182d737..b2bc966 100644
--- a/src/model/GModelSpatialComposite.cpp
+++ b/src/model/GModelSpatialComposite.cpp
@@ -489,7 +489,7 @@ void GModelSpatialComposite::write(GXmlElement& xml) const
  ***************************************************************************/
 void GModelSpatialComposite::append(const GModelSpatial& component,
                                     const std::string&   name,
-                                    double scale)
+                                    const double& scale)
 {
     // Append model container
     m_components.push_back(component.clone());