diff --git a/openmc/material.py b/openmc/material.py
index 4100c26ecf..9fc99c26a8 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -193,7 +193,7 @@ class Material(object):
                        name, basestring)
             self._name = name
         else:
-            self._name = None
+            self._name = ''
 
     def set_density(self, units, density=NO_DENSITY):
         """Set the density of the material
diff --git a/openmc/mesh.py b/openmc/mesh.py
index 822370c019..3b66076b79 100644
--- a/openmc/mesh.py
+++ b/openmc/mesh.py
@@ -155,7 +155,7 @@ class Mesh(object):
                        name, basestring)
             self._name = name
         else:
-            self._name = None
+            self._name = ''
 
     @type.setter
     def type(self, meshtype):
diff --git a/openmc/surface.py b/openmc/surface.py
index ed446c3749..279246b029 100644
--- a/openmc/surface.py
+++ b/openmc/surface.py
@@ -128,7 +128,7 @@ class Surface(object):
             check_type('surface name', name, basestring)
             self._name = name
         else:
-            self._name = None
+            self._name = ''
 
     @boundary_type.setter
     def boundary_type(self, boundary_type):
diff --git a/openmc/tallies.py b/openmc/tallies.py
index 5755187346..0661ab67b1 100644
--- a/openmc/tallies.py
+++ b/openmc/tallies.py
@@ -420,7 +420,7 @@ class Tally(object):
             cv.check_type('tally name', name, basestring)
             self._name = name
         else:
-            self._name = None
+            self._name = ''
 
     def add_filter(self, filter):
         """Add a filter to the tally
diff --git a/openmc/universe.py b/openmc/universe.py
index b38ff2c4ba..b74dde656d 100644
--- a/openmc/universe.py
+++ b/openmc/universe.py
@@ -153,7 +153,7 @@ class Cell(object):
             cv.check_type('cell name', name, basestring)
             self._name = name
         else:
-            self._name = None
+            self._name = ''
 
     @fill.setter
     def fill(self, fill):
@@ -472,7 +472,7 @@ class Universe(object):
             cv.check_type('universe name', name, basestring)
             self._name = name
         else:
-            self._name = None
+            self._name = ''
 
     def add_cell(self, cell):
         """Add a cell to the universe.
@@ -732,7 +732,7 @@ class Lattice(object):
             cv.check_type('lattice name', name, basestring)
             self._name = name
         else:
-            self._name = None
+            self._name = ''
 
     @outer.setter
     def outer(self, outer):
diff --git a/tests/test_track_output/results_test.dat b/tests/test_track_output/results_test.dat
new file mode 100644
index 0000000000..6ded87a0ec
--- /dev/null
+++ b/tests/test_track_output/results_test.dat
@@ -0,0 +1,9 @@
+<?xml version="1.0"?>
+<VTKFile type="PPolyData" version="0.1" byte_order="LittleEndian" compressor="vtkZLibDataCompressor">
+  <PPolyData GhostLevel="0">
+    <PPoints>
+      <PDataArray type="Float32" Name="Points" NumberOfComponents="3"/>
+    </PPoints>
+    <Piece Source="poly_0.vtp"/>
+  </PPolyData>
+</VTKFile>