diff --git a/test/test_git.py b/test/test_git.py
index 5bcf89bdd..4a54d0d9b 100644
--- a/test/test_git.py
+++ b/test/test_git.py
@@ -773,6 +773,7 @@ def stderr_handler(line):
 
         cmdline = [
             sys.executable,
+            "-S",  # Keep any `CoverageWarning` messages out of the subprocess stderr.
             fixture_path("cat_file.py"),
             str(fixture_path("issue-301_stderr")),
         ]