diff --git a/tests/unit_tests/test_filters.py b/tests/unit_tests/test_filters.py
index d52775abd2..ea94a600e3 100644
--- a/tests/unit_tests/test_filters.py
+++ b/tests/unit_tests/test_filters.py
@@ -47,7 +47,7 @@ def test_cell_instance():
 
 
 def test_collision():
-    f = openmc.CollisionFilter([1,5,3,2,8])
+    f = openmc.CollisionFilter([1, 5, 3, 2, 8])
     assert f.bins[0] == 1
     assert f.bins[1] == 5
     assert f.bins[-1] == 8