diff --git a/trees/bt_is_same_trees.py b/trees/bt_is_same_trees.py
index f814aa9..8cd7a28 100644
--- a/trees/bt_is_same_trees.py
+++ b/trees/bt_is_same_trees.py
@@ -11,4 +11,4 @@ def is_same_trees(p, q):
         if (not p and q) or (not q and p) or p.val != q.val:
             return False
         
-        return self.is_same_trees(p.right, q.right) and self.is_same_trees(p.left, q.left)
+        return is_same_trees(p.right, q.right) and is_same_trees(p.left, q.left)