diff --git a/tests/test_solver.py b/tests/test_solver.py
index 2211b50..1720ef3 100644
--- a/tests/test_solver.py
+++ b/tests/test_solver.py
@@ -60,7 +60,7 @@ def heat_balance(currents: np.array):
         xmax=np.array([10_000, 10_000]),
         tolerance=1e-8,
     )
-    np.testing.assert_array_almost_equal(solution, [9000, 9000], decimal=8)
+    np.testing.assert_array_almost_equal(solution, [9_000, 9_000], decimal=8)
 
 
 def test_bisect_raises_valueerror_when_same_sign_for_array_input():