diff --git a/python/tests/test_genotype_matching_fb.py b/python/tests/test_genotype_matching_fb.py
index 71ad3ad86d..248382e913 100644
--- a/python/tests/test_genotype_matching_fb.py
+++ b/python/tests/test_genotype_matching_fb.py
@@ -1,11 +1,11 @@
 import copy
 import itertools
+
 import lshmm as ls
 import msprime
 import numpy as np
+
 import tskit
-import copy
-from math import isclose
 
 EQUAL_BOTH_HOM = 4
 UNEQUAL_BOTH_HOM = 0
@@ -346,7 +346,6 @@ def update_tree(self):
                     vt.tree_node = -1
                 vt.value_index = -1
 
-
         self.N = np.zeros(self.tree.tree_sequence.num_nodes, dtype=int)
         node_map = {st.tree_node: st for st in self.T}