diff --git a/SL/IR.pm b/SL/IR.pm
index b42c2566f1..fd8ade4a76 100644
--- a/SL/IR.pm
+++ b/SL/IR.pm
@@ -262,8 +262,11 @@ sub _post_invoice {
       # change lastcost for part and all assemblies and assortments recursively
       my $a = SL::DB::Part->load_cached(conv_i($form->{"id_$i"}));
       my $part_price_factor = $a->price_factor_id ? $a->price_factor->factor : 1;
-      $a->update_attributes(lastcost => abs($fxsellprice * $form->{exchangerate} / $basefactor / $price_factor * $part_price_factor));
-      $a->set_lastcost_assemblies_and_assortiments;
+      my $new_lastcost      = abs($fxsellprice * $form->{exchangerate} / $basefactor / $price_factor * $part_price_factor);
+      if ( abs($a->lastcost - $new_lastcost) >= 0.009 ) {
+        $a->update_attributes(lastcost => $new_lastcost);
+        $a->set_lastcost_assemblies_and_assortiments;
+      }
 
       # check if we sold the item already and
       # make an entry for the expense and inventory