1 files changed, 2 insertions, 2 deletions
diff --git a/collect/bst.py b/collect/bst.py
index 9d65259..8602ce6 100644
--- a/collect/bst.py
+++ b/collect/bst.py
@@ -520,12 +520,12 @@ class BinarySearchTree(object):
             return x
 
         path = self.parent_path(node)
-        assert path[-1]
+        assert path[-1] is not None
         assert path[-1] == node
         path = path[:-1]
         path.reverse()
         for ancestor in path:
-            assert ancestor
+            assert ancestor is not None
             if node != ancestor.right:
                 return ancestor
             node = ancestor