diff --git a/Ball.cpp b/Ball.cpp
index 7f6c0f0..5851b5a 100644
--- a/Ball.cpp
+++ b/Ball.cpp
@@ -5,7 +5,7 @@
 Ball::Ball(const Point& _center, double _min_height, double _v_x, double _v_z,
         double _p, double _q) :
     Center(_center),
-    surface(_center, min_height, _p, _q),
+    surface(_center, _min_height, _p, _q),
     init_h(_center.y),
     min_height(_min_height),
     bounce_number(0.0),