diff --git a/python/tests/test_material_grid.py b/python/tests/test_material_grid.py
index d8750987a..25b6b4b50 100644
--- a/python/tests/test_material_grid.py
+++ b/python/tests/test_material_grid.py
@@ -159,7 +159,7 @@ def test_subpixel_smoothing(self):
     def test_symmetry(self):
             tran_nosym = compute_transmittance(False)
             tran_sym = compute_transmittance(True)
-            self.assertAlmostEqual(tran_nosym, tran_sym)
+            self.assertAlmostEqual(tran_nosym, tran_sym, places=6)
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/src/monitor.cpp b/src/monitor.cpp
index 6ed10205c..46082332f 100644
--- a/src/monitor.cpp
+++ b/src/monitor.cpp
@@ -178,7 +178,7 @@ complex<double> fields::get_chi1inv(component c, direction d, const ivec &origlo
                             0);
         return parallel ? sum_to_all(val) : val;
       }
-  return d == component_direction(c) ? 1.0 : 0; // default to vacuum outside computational cell
+  return d == component_direction(c) && (parallel || am_master()) ? 1.0 : 0; // default to vacuum outside computational cell
 }
 
 complex<double> fields_chunk::get_chi1inv(component c, direction d, const ivec &iloc,