diff --git a/src/grid_mod.F90 b/src/grid_mod.F90
index aa4f58b97ccdff840100b178a3684f2faa9ae692..177999be859a248d02abb776d264ce3d86ef0545 100644
--- a/src/grid_mod.F90
+++ b/src/grid_mod.F90
@@ -512,6 +512,7 @@ CONTAINS
     ! Ghosts boundaries (depend on the order of z operators)
     IF(Nz .EQ. 1) THEN
       izgs = izs;     izge = ize;
+      zarray(izs) = 0; zarray_full(izs) = 0;
     ELSEIF(Nz .GE. 4) THEN
       izgs = izs - 2; izge = ize + 2;
     ELSE