diff --git a/engine/inc/physics/ray.hpp b/engine/inc/physics/ray.hpp
index 85eac67..bbfcbea 100644
--- a/engine/inc/physics/ray.hpp
+++ b/engine/inc/physics/ray.hpp
@@ -49,7 +49,7 @@ class Ray {
    * @return Vec4 point of intersection
    */
   bool intersectBox(const Vec4& minCorner, const Vec4& maxCorner,
-                    float& distance) const;
+                    const float& distance) const;
 
   /** Returns inverse direction */
   Vec4 invDir() const;
diff --git a/engine/src/physics/ray.cpp b/engine/src/physics/ray.cpp
index d91d9f2..9cc7ab2 100644
--- a/engine/src/physics/ray.cpp
+++ b/engine/src/physics/ray.cpp
@@ -32,7 +32,7 @@ float Ray::distanceToPoint(const Vec4& point) const {
 }
 
 bool Ray::intersectBox(const Vec4& minCorner, const Vec4& maxCorner,
-                       float& distance) const {
+                       const float& distance) const {
   auto inv = invDir();
   inv.normalize();