diff --git a/src/tree.py b/src/tree.py
index 62ba9ad3c88d05efdd17bebd5a8d27cff4c5b2e6..904abd6716d68c7961048ceee4eb9ecd1a6f1171 100644
--- a/src/tree.py
+++ b/src/tree.py
@@ -243,8 +243,12 @@ class TreeWalker:
         return config
 
     def ensure_node_id(self, config):
-        if "node_id" not in config:
-            config["node_id"] = self.gen_node_id()
+        if "node_id" not in config or \
+                not config["node_id"].startswith(f"{self.tree}-") or \
+                config["node_id"] in id_set:
+            new_id = self.gen_node_id()
+            id_set.add(new_id)
+            config["node_id"] = new_id
             return True, config
         else:
             return False, config