diff --git a/src/ZSOLVER/tensorproductmultigrid_Source/communication.f90 b/src/ZSOLVER/tensorproductmultigrid_Source/communication.f90
index 794ac3a6f7c58f7c1bfdfb1baf02ed5b37386273..e2f8661ff31818833c01000a0eb47a24451a4556 100644
--- a/src/ZSOLVER/tensorproductmultigrid_Source/communication.f90
+++ b/src/ZSOLVER/tensorproductmultigrid_Source/communication.f90
@@ -547,12 +547,14 @@ contains
         end if
         if (LUseT) then
            local_sumt = 0.0_rl
+           za_st => a%st
+           zb_st => b%st
            !$acc kernels loop collapse(3)
            do iz=0,nz+1
               do iy=a%icompy_min,a%icompy_max
                  do ix=a%icompx_min,a%icompx_max
                     local_sumt = local_sumt &
-                         + a%st(ix,iy,iz)*b%st(ix,iy,iz)
+                         + za_st(ix,iy,iz)*zb_st(ix,iy,iz)
                  end do
               end do
            end do