diff --git a/floorshapes.cpp b/floorshapes.cpp
index 85426c0e..570038df 100644
--- a/floorshapes.cpp
+++ b/floorshapes.cpp
@@ -327,6 +327,7 @@ namespace gp {
     cellwalker cw(c, i);
     cw += wstep;
     transmatrix cwm = shmup::calc_relative_matrix(cw.c, c);
+    if(elliptic && cwm[2][2] < 0) cwm = centralsym * cwm;
     return cwm * C0;
     }
   
@@ -334,6 +335,7 @@ namespace gp {
     cellwalker cw(c, i);
     cw += wstep;
     transmatrix cwm = shmup::calc_relative_matrix(cw.c, c);
+    if(elliptic && cwm[2][2] < 0) cwm = centralsym * cwm;
     auto li1 = get_local_info(cw.c);
     return cwm * get_corner_position(li1, (cw+2).spin);
     }