diff --git a/src/Shapes/Capsule.h b/src/Shapes/Capsule.h
index f0a654cbc..bceb0876c 100644
--- a/src/Shapes/Capsule.h
+++ b/src/Shapes/Capsule.h
@@ -41,6 +41,8 @@ namespace Magnum { namespace Shapes {
 Unlike other elements the capsule expects uniform scaling. See @ref shapes for
 brief introduction.
 @see Capsule2D, Capsule3D
+@todo Store the radius as squared value to avoid sqrt/pow? Will complicate
+    collision detection with sphere.
 */
 template<UnsignedInt dimensions> class MAGNUM_SHAPES_EXPORT Capsule {
     public:
diff --git a/src/Shapes/Sphere.h b/src/Shapes/Sphere.h
index 44f7faa03..17d27bdd0 100644
--- a/src/Shapes/Sphere.h
+++ b/src/Shapes/Sphere.h
@@ -41,6 +41,8 @@ namespace Magnum { namespace Shapes {
 Unlike other elements the sphere expects uniform scaling. See @ref shapes for
 brief introduction.
 @see Sphere2D, Sphere3D
+@todo Store the radius as squared value to avoid sqrt/pow? Will complicate
+    collision detection with another sphere.
 */
 template<UnsignedInt dimensions> class MAGNUM_SHAPES_EXPORT Sphere {
     public: