--- a/+multiblock/DiffOp.m	Fri Jul 15 11:22:12 2016 +0200
+++ b/+multiblock/DiffOp.m	Fri Jul 15 13:46:05 2016 +0200
@@ -57,12 +57,13 @@
             end
 
             for i = 1:nBlocks
-                for j = i:nBlocks
+                for j = 1:nBlocks
                     intf = grid.connections{i,j};
                     if isempty(intf)
                         continue
                     end
 
+
                     [ii, ij] = obj.diffOps{i}.interface(intf{1}, obj.diffOps{j}, intf{2});
                     D{i,i} = D{i,i} + ii;
                     D{i,j} = D{i,j} + ij;