diff --git a/tests/test_helper.py b/tests/test_helper.py
index a42407bd..3035a535 100644
--- a/tests/test_helper.py
+++ b/tests/test_helper.py
@@ -170,6 +170,8 @@ def test_number_to_string_decimal_digits(self, t1, t2, significant_digits, numbe
                                  (-0.00002-0.00002j, 0.00001+0.00001j, 0, "e", True),
                                  # negative imaginary parts must round-trip, not raise (issue #551)
                                  (1-1j, 2-3j, 1, "f", ('1.0-1.0j', '2.0-3.0j')),
+                                 (1-1j, 1.2-1.2j, 1, "e", ('1.0e+0-1.0e+0j', '1.2e+0-1.2e+0j')),
+                                 (-1-1j, -1.2-1.2j, 1, "f", ('-1.0-1.0j', '-1.2-1.2j')),
                                  (4-10j, 4.0000002-10.0000002j, 5, "f", True),
                                  (10j, 10.2j, 5, "f", ('0.00000+10.00000j', '0.00000+10.20000j')),
                                  (10j, 10.2j, 5, "e", ('0.00000e+0+1.00000e+1j', '0.00000e+0+1.02000e+1j')),