diff --git a/matlab/get_grids_1d.m b/matlab/get_grids_1d.m
index c56f9f1dd6bba8a434b0a4c42245b39aa431a768..f89a3b0f1329de4d04fabacbe522d7076157678b 100644
--- a/matlab/get_grids_1d.m
+++ b/matlab/get_grids_1d.m
@@ -63,7 +63,7 @@ if (isempty(rhotor_norm.x) ||isempty(rhotor_norm.t) || isempty(rhotor_norm.data)
 end
 it_rt = iround_os(rhotor_norm.t,gdat_data.t);
 it_vol = iround_os(rhovol.t,gdat_data.t);
-tens0=0.;
+tens0=0.; % need value of tension even if =0 so that interpos OK with only one xout point
 for it=1:length(gdat_data.t)
   % do an interpolation on closest point to avoid 2D interp
   it_rt_eff = it_rt(it);