diff --git a/tests/test_git.py b/tests/test_git.py
index b7e15f59..616cd440 100644
--- a/tests/test_git.py
+++ b/tests/test_git.py
@@ -43,5 +43,5 @@ def test_git_missing_repo(self):
     def test_git_private_repo(self):
         """Check we get the right exception when credentials are required."""
         self.assertRaises(RuntimeError, git, (
-            "ls-remote", "-ht", PRIVATE_REPO,
+            "-c", "credential.helper=", "ls-remote", "-ht", PRIVATE_REPO,
         ), prompt=False)