diff --git a/swh/loader/cvs/tests/test_cvsclient.py b/swh/loader/cvs/tests/test_cvsclient.py
index bb99fbf..7e7163c 100644
--- a/swh/loader/cvs/tests/test_cvsclient.py
+++ b/swh/loader/cvs/tests/test_cvsclient.py
@@ -1,30 +1,31 @@
 # Copyright (C) 2022  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU Affero General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 from urllib.parse import urlparse
 
 from swh.loader.cvs.cvsclient import CVSClient
 
 
 def test_cvs_client_rlog_could_not_read_rcs_file(mocker):
 
     url = "ssh://anoncvs@anoncvs.example.org/cvsroot/src"
     file = "src/README.txt"
 
     mocker.patch("swh.loader.cvs.cvsclient.socket")
+    mocker.patch("swh.loader.cvs.cvsclient.subprocess")
     conn_read_line = mocker.patch.object(CVSClient, "conn_read_line")
     conn_read_line.side_effect = [
         # server response lines when client is initialized
         b"Valid-requests ",
         b"ok\n",
         # server response lines when attempting to fetch rlog of a file
         # but RCS file is missing
         f"E cvs rlog: could not read RCS file for {file}\n".encode(),
         b"ok\n",
     ]
 
     client = CVSClient(urlparse(url))
 
     assert client.fetch_rlog(file.encode()) is None