diff --git a/sphere.cpp b/sphere.cpp
index 88062a47..1d628132 100644
--- a/sphere.cpp
+++ b/sphere.cpp
@@ -172,6 +172,8 @@ struct hrmap_spherical : hrmap_standard {
     return Id;
     }
   
+  void on_dim_change() override { where.clear(); }
+
   transmatrix relative_matrixc(cell *c2, cell *c1, const hyperpoint& hint) override {
     transmatrix T = iso_inverse(get_where(c1)) * get_where(c2);
     if(elliptic) fixelliptic(T);