diff --git a/code/math.f90 b/code/math.f90
index 18e31f1f0..552b1b31d 100644
--- a/code/math.f90
+++ b/code/math.f90
@@ -2808,8 +2808,9 @@ pure function math_rotate_forward3333(tensor,rot_tensor)
 
  do i = 1_pInt,3_pInt; do j = 1_pInt,3_pInt; do k = 1_pInt,3_pInt; do l = 1_pInt,3_pInt
    do m = 1_pInt,3_pInt; do n = 1_pInt,3_pInt; do o = 1_pInt,3_pInt; do p = 1_pInt,3_pInt
-     math_rotate_forward3333(i,j,k,l) = tensor(i,j,k,l)+rot_tensor(m,i)*rot_tensor(n,j)*&
-                                                           rot_tensor(o,k)*rot_tensor(p,l)*tensor(m,n,o,p)
+     math_rotate_forward3333(i,j,k,l) = math_rotate_forward3333(i,j,k,l) &
+                                      + rot_tensor(m,i) * rot_tensor(n,j) &
+                                      * rot_tensor(o,k) * rot_tensor(p,l) * tensor(m,n,o,p)
  enddo; enddo; enddo; enddo; enddo; enddo; enddo; enddo
 
 end function math_rotate_forward3333