diff --git a/test/test_bytes2human.py b/test/test_bytes2human.py
index db3acf6a4..6741ab543 100644
--- a/test/test_bytes2human.py
+++ b/test/test_bytes2human.py
@@ -96,3 +96,8 @@ class Testbytes2human(PicardTestCase):
             lines = [l.rstrip("\n") for l in f.readlines()]
             f.close()
             return lines
+
+    def test_calc_unit(self):
+        self.assertEqual(bytes2human.calc_unit(12456, 1024), (12.1640625, 'KiB'))
+        self.assertEqual(bytes2human.calc_unit(-12456, 1000), (-12.456, 'kB'))
+        self.assertRaises(ValueError, bytes2human.calc_unit, 0, 1001)