diff --git a/openmc/mesh.py b/openmc/mesh.py
index c490f604a..d2a93676f 100644
--- a/openmc/mesh.py
+++ b/openmc/mesh.py
@@ -10,6 +10,7 @@ import openmc.checkvalue as cv
 import openmc
 from openmc._xml import get_text
 from openmc.mixin import IDManagerMixin
+from openmc.surface import _BOUNDARY_TYPES
 
 
 class MeshBase(IDManagerMixin, metaclass=ABCMeta):
@@ -322,7 +323,7 @@ class RegularMesh(MeshBase):
 
         return mesh
 
-    def build_cells(self, bc=['reflective'] * 6):
+    def build_cells(self, bc=None):
         """Generates a lattice of universes with the same dimensionality
         as the mesh object.  The individual cells/universes produced
         will not have material definitions applied and so downstream code
@@ -330,12 +331,13 @@ class RegularMesh(MeshBase):
 
         Parameters
         ----------
-        bc : iterable of {'reflective', 'periodic', 'transmission', or 'vacuum'}
+        bc : iterable of {'reflective', 'periodic', 'transmission', 'vacuum', or 'white'}
             Boundary conditions for each of the four faces of a rectangle
-            (if aplying to a 2D mesh) or six faces of a parallelepiped
+            (if applying to a 2D mesh) or six faces of a parallelepiped
             (if applying to a 3D mesh) provided in the following order:
             [x min, x max, y min, y max, z min, z max].  2-D cells do not
-            contain the z min and z max entries.
+            contain the z min and z max entries. Defaults to 'reflective' for
+            all faces.
 
         Returns
         -------
@@ -349,11 +351,12 @@ class RegularMesh(MeshBase):
             geometry.
 
         """
-
-        cv.check_length('bc', bc, length_min=4, length_max=6)
+        if bc is None:
+            bc = ['reflective'] * 6
+        if len(bc) not in (4, 6):
+            raise ValueError('Boundary condition must be of length 4 or 6')
         for entry in bc:
-            cv.check_value('bc', entry, ['transmission', 'vacuum',
-                                         'reflective', 'periodic'])
+            cv.check_value('bc', entry, _BOUNDARY_TYPES)
 
         n_dim = len(self.dimension)
 
@@ -390,7 +393,7 @@ class RegularMesh(MeshBase):
         # We will concurrently build cells to assign to these universes
         cells = []
         universes = []
-        for index in self.indices:
+        for _ in self.indices:
             cells.append(openmc.Cell())
             universes.append(openmc.Universe())
             universes[-1].add_cell(cells[-1])