diff --git a/src/libslic3r/GCode/WipeTower.hpp b/src/libslic3r/GCode/WipeTower.hpp
index e14f61391..d4c802140 100644
--- a/src/libslic3r/GCode/WipeTower.hpp
+++ b/src/libslic3r/GCode/WipeTower.hpp
@@ -188,6 +188,7 @@ public:
     float get_depth() const { return m_wipe_tower_depth; }
     float get_brim_width() const { return m_wipe_tower_brim_width_real; }
     BoundingBoxf get_bbx() const {
+        if (m_outer_wall.empty()) return BoundingBoxf({Vec2d(0,0)});
         BoundingBox  box = get_extents(m_outer_wall.begin()->second);
         BoundingBoxf res = BoundingBoxf(unscale(box.min), unscale(box.max));
         res.translate(m_rib_offset.cast<double>());