diff --git a/src/objectSphere.hh b/src/objectSphere.hh
index 7ad62d1..e5e9499 100644
--- a/src/objectSphere.hh
+++ b/src/objectSphere.hh
@@ -27,8 +27,8 @@ public:
     void Write(std::ostream& ost) const;
 
 protected:
-    bool DoIntersect(const basics::Ray& ray, TVector& t, Stats& stats) const;
-    basics::Vector4 DoNormal(const basics::Vector4& p) const;
+    bool DoIntersect(const basics::Ray& ray, TVector& t, Stats& stats) const override;
+    basics::Vector4 DoNormal(const basics::Vector4& p) const override;
 
 private:
     Double mRadius;