diff --git a/tests/test_dicom.py b/tests/test_dicom.py
index 5354e86e27be21a08af90cc5dc2b4392f7e4c23a..e3b444c3c6c535416c86c7a690b5e4e37d2c8d9e 100644
--- a/tests/test_dicom.py
+++ b/tests/test_dicom.py
@@ -145,8 +145,8 @@ def test_sersiesCRC():
     for series, expect in tests:
         series = dict(series)
         if expect is RANDOM:
-            expect = ''.join(random.choices(
-                string.ascii_letters + string.digits, k=30))
+            expect = ''.join([random.choice(string.ascii_letters + string.digits)
+                              for i in range(30)])
             series['SeriesInstanceUID'] = expect
             expect = str(binascii.crc32(expect.encode()))
         echo = series.get('EchoNumber', 0)