diff --git a/shapes/Cyl.cc b/shapes/Cyl.cc
index a8dc515..aafe022 100644
--- a/shapes/Cyl.cc
+++ b/shapes/Cyl.cc
@@ -45,7 +45,7 @@ Shape::IntersectList Cyl::intersect(const Ray & ray)
     if (m_top_radius > 0.0)
     {
         LinearSolver solver(ray_inv.getDirection()[2],
-                            ray_inv.getOrigin()[2] + m_height);
+                            ray_inv.getOrigin()[2] - m_height);
         Solver::Result solutions = solver.solve();
         if (solutions.numResults > 0)
         {