diff --git a/tests/obs_test.py b/tests/obs_test.py
index c2d161e4..8f32bd77 100644
--- a/tests/obs_test.py
+++ b/tests/obs_test.py
@@ -521,6 +521,9 @@ def test_intersection_idx():
     assert pe.obs._intersection_idx([range(10, 1010, 10), range(10, 1010, 50)]) == range(10, 1010, 50)
     assert pe.obs._intersection_idx([range(500, 6050, 50), range(500, 6250, 250)]) == range(500, 6050, 250)
 
+    for ids in [[list(range(1, 80, 3)), list(range(1, 100, 2))], [range(1, 80, 3), range(1, 100, 2), range(1, 100, 7)]]:
+        assert list(pe.obs._intersection_idx(ids)) == pe.obs._intersection_idx([list(o) for o in ids])
+
 
 def test_intersection_collapse():
     range1 = range(1, 2000, 2)