diff --git a/openmc/geometry.py b/openmc/geometry.py
index 8815f2c8380..175cef2bf37 100644
--- a/openmc/geometry.py
+++ b/openmc/geometry.py
@@ -701,7 +701,7 @@ def remove_redundant_surfaces(self) -> typing.Dict[int, openmc.Surface]:
             coeffs = tuple(round(surf._coefficients[k],
                                  self.surface_precision)
                            for k in surf._coeff_keys)
-            key = (surf._type,) + coeffs
+            key = (surf._type, surf._boundary_type) + coeffs
             redundancies[key].append(surf)
 
         redundant_surfaces = {replace.id: keep
diff --git a/tests/unit_tests/test_geometry.py b/tests/unit_tests/test_geometry.py
index f5a1bd7db69..6cc577c820c 100644
--- a/tests/unit_tests/test_geometry.py
+++ b/tests/unit_tests/test_geometry.py
@@ -390,3 +390,16 @@ def test_get_all_nuclides():
     c2 = openmc.Cell(fill=m2, region=+s)
     geom = openmc.Geometry([c1, c2])
     assert geom.get_all_nuclides() == ['Be9', 'Fe56']
+
+
+def test_redundant_surfaces():
+    # Make sure boundary condition is accounted for
+    s1 = openmc.Sphere(r=5.0)
+    s2 = openmc.Sphere(r=5.0, boundary_type="vacuum")
+    c1 = openmc.Cell(region=-s1)
+    c2 = openmc.Cell(region=+s1)
+    u_lower = openmc.Universe(cells=[c1, c2])
+    c3 = openmc.Cell(fill=u_lower, region=-s2)
+    geom = openmc.Geometry([c3])
+    redundant_surfs = geom.remove_redundant_surfaces()
+    assert len(redundant_surfs) == 0