--- ./src/ElementCollision.h.orig	2018-01-29 21:56:58.057957000 +0100
+++ ./src/ElementCollision.h	2018-01-29 22:04:08.902625000 +0100
@@ -30,7 +30,7 @@
 using namespace std;
 
 class Balle;
-class Struct_Collision;
+struct Struct_Collision;
 
 class Point
 {