diff --git a/test/test_LensModel/test_Profiles/test_sersic_utils.py b/test/test_LensModel/test_Profiles/test_sersic_utils.py
new file mode 100644
index 000000000..a23fead01
--- /dev/null
+++ b/test/test_LensModel/test_Profiles/test_sersic_utils.py
@@ -0,0 +1,11 @@
+import numpy as np
+from lenstronomy.LensModel.Profiles.sersic_utils import SersicUtil
+import numpy.testing as npt
+
+
+def test_bn():
+    n_array = np.linspace(start=0.2, stop=8, num=30)
+    for n in n_array:
+        bn_approx = 1.9992 * n - 0.3271
+        bn = SersicUtil.b_n(n)
+        npt.assert_almost_equal(bn, bn_approx, decimal=3)