diff --git a/sources/evolution.F90 b/sources/evolution.F90
index 94a0d30..852212a 100644
--- a/sources/evolution.F90
+++ b/sources/evolution.F90
@@ -4205,15 +4205,23 @@ module evolution
 
     integer, intent(in) :: nh, nl
 
-    integer :: l, n, p
-    real(kind=8) :: fnorm, err
-
     type(block_data), pointer :: pdata
 
+    integer      :: l, n, p
+    real(kind=8) :: err
+
+    logical     , save :: first = .true.
+    real(kind=8), save :: fnorm = 1.0d+00
+
 !-------------------------------------------------------------------------------
 !
+    if (first) then
+      fnorm = 1.0d+00 / ncells**NDIMS
+
+      first = .false.
+    end if
+
     errors(:) = 0.0d+00
-    fnorm     = 1.0d+00 / (get_nleafs() * ncells**NDIMS)
 
     n = get_dblocks()
 
@@ -4233,7 +4241,7 @@ module evolution
                    abs(pdata%uu(p,nb:ne,nb:ne,  :  ,nl)))))**2)
 #endif /* NDIMS == 3 */
 !$omp atomic update
-        errors(p) = errors(p) + err
+        errors(p) = errors(p) + fnorm * err
       end do
     end do
 !$omp end parallel do
@@ -4242,7 +4250,7 @@ module evolution
     call reduce_sum(errors)
 #endif /* MPI */
 
-    errors(:) = sqrt(fnorm * errors(:))
+    errors(:) = sqrt(errors(:) / get_nleafs())
 
 !-------------------------------------------------------------------------------
 !