1diff --git a/testing/functional/__init__.py b/testing/functional/__init__.py
2index 6c82d2c7..22163fa3 100644
3--- a/testing/functional/__init__.py
4+++ b/testing/functional/__init__.py
5@@ -94,8 +94,8 @@ class FunctionalTestCase(DuplicityTestCase):
6 for item in passphrase_input:
7 assert isinstance(item, str), f"item {os.fsdecode(item)} in passphrase_input is not unicode"
8
9- # set python path to be dev directory
10- os.environ["PYTHONPATH"] = _top_dir
11+ # prepend dev directory to python path
12+ os.environ["PYTHONPATH"] = _top_dir + ":" + os.environ["PYTHONPATH"]
13
14 cmd_list = []
15