diff --git a/Sample/Particle/Particle.h b/Sample/Particle/Particle.h
index 6b22e73500a0fc582b92bc3be497f2155625ccb4..43187bf986a4a4af1aab4e1500b3825eabb7dc90 100644
--- a/Sample/Particle/Particle.h
+++ b/Sample/Particle/Particle.h
@@ -39,7 +39,7 @@ public:
 
     const IFormFactor* formFactor() const { return m_form_factor.get(); }
 
-protected:
+private:
     Material m_material;
     std::unique_ptr<IFormFactor> m_form_factor;
 };