diff --git a/tests/pytest.ini b/tests/pytest.ini
index 5fc918b..1a29fde 100644
--- a/tests/pytest.ini
+++ b/tests/pytest.ini
@@ -1,2 +1,4 @@
 [pytest]
 addopts = -m 'not nonfree'
+markers =
+    nonfree: marks tests as requiring nonfree (i.e., having restrictive licenses) dependencies