diff --git a/launcher/tests/fixtures/bad-os-release-file b/launcher/tests/fixtures/bad-os-release-file
new file mode 100644
index 000000000..eca68dfc5
--- /dev/null
+++ b/launcher/tests/fixtures/bad-os-release-file
@@ -0,0 +1,4 @@
+# No line
+VERSION=
+[we're doing toml now]
+RELEASES = [ ["gamma", "delta"], [1, 2] ]
diff --git a/launcher/tests/test_util.py b/launcher/tests/test_util.py
index 7488093fd..c9660bb0e 100644
--- a/launcher/tests/test_util.py
+++ b/launcher/tests/test_util.py
@@ -237,6 +237,7 @@ def test_detect_qubes(
         ("os-release-qubes-4.1", 5),
         ("os-release-ubuntu", 4),
         ("no-such-file", 4),
+        ("bad-os-release-file", 4),
     ],
 )
 @mock.patch("Util.sdlog.error")
@@ -283,5 +284,7 @@ def test_pick_bad_qt(
     version via environment override
     """
     mocked_env = {"SDW_UPDATER_QT": env_override}
-    with mock.patch.dict("os.environ", mocked_env), pytest.raises(ValueError):
+    with mock.patch.dict("os.environ", mocked_env), mock.patch(
+        "Util.OS_RELEASE_FILE", os.path.join(FIXTURES_PATH, "os-release-qubes-4.0")
+    ), pytest.raises(ValueError):
         util.get_qt_version()