diff --git a/tests/test-ancestor.py b/tests/test-ancestor.py
--- a/tests/test-ancestor.py
+++ b/tests/test-ancestor.py
@@ -91,6 +91,10 @@ def test_lazyancestors():
     s = genlazyancestors([11, 13])
     printlazyancestors(s, [11, 13, 7, 9, 8, 3, 6, 4, 1, -1, 0])
 
+    # Standard with ancestry in the initial set (1 is ancestor of 3)
+    s = genlazyancestors([1, 3])
+    printlazyancestors(s, [1, -1, 0])
+
     # Including revs
     s = genlazyancestors([11, 13], inclusive=True)
     printlazyancestors(s, [11, 13, 7, 9, 8, 3, 6, 4, 1, -1, 0])
diff --git a/tests/test-ancestor.py.out b/tests/test-ancestor.py.out
--- a/tests/test-ancestor.py.out
+++ b/tests/test-ancestor.py.out
@@ -38,6 +38,8 @@
 []
 % lazy ancestor set for [11, 13], stoprev = 0, inclusive = False
 [7, 8, 3, 4, 1, 0]
+% lazy ancestor set for [1, 3], stoprev = 0, inclusive = False
+[1, 0]
 % lazy ancestor set for [11, 13], stoprev = 0, inclusive = True
 [11, 13, 7, 8, 3, 4, 1, 0]
 % lazy ancestor set for [11, 13], stoprev = 6, inclusive = False