diff --git a/src/utils/openmc/material.py b/src/utils/openmc/material.py
index 7034feb6ea..914cb154a1 100644
--- a/src/utils/openmc/material.py
+++ b/src/utils/openmc/material.py
@@ -224,7 +224,7 @@ class Material(object):
         warnings.warn('This feature is not yet implemented in a release ' \
                       'version of openmc')
 
-        if not is_string(name):
+        if not is_string(name) and not name is None:
             msg = 'Unable to add OTF material file to Material ID={0} with a ' \
                         'non-string name {1}'.format(self._id, name)
             raise ValueError(msg)