diff --git a/modules/06_oop_basics/src/inheritance.cpp b/modules/06_oop_basics/src/inheritance.cpp
index afc0143..847c630 100644
--- a/modules/06_oop_basics/src/inheritance.cpp
+++ b/modules/06_oop_basics/src/inheritance.cpp
@@ -2,11 +2,12 @@
 
 namespace oop {
 
-Circle::Circle(double radius) : radius_(radius) {}
+Circle::Circle(const double radius) : radius_(radius) {}
+
 auto Circle::name() const -> std::string { return "Circle"; }
 auto Circle::area() const -> double { return 3.141592653589793 * radius_ * radius_; }
 
-Rectangle::Rectangle(double width, double height) : width_(width), height_(height) {}
+Rectangle::Rectangle(const double width, const double height) : width_(width), height_(height) {}
 auto Rectangle::name() const -> std::string { return "Rectangle"; }
 auto Rectangle::area() const -> double { return width_ * height_; }