diff --git a/tools/python/jwutils/stree/StringTree.py b/tools/python/jwutils/stree/StringTree.py
index 9e66cbf..64e46e9 100644
--- a/tools/python/jwutils/stree/StringTree.py
+++ b/tools/python/jwutils/stree/StringTree.py
@@ -104,8 +104,13 @@ class StringTree: # export
         if l > 1:
             assert len(rest) > 0
             return self.children[nibble].__set(rest, content=content)
+        # last component, a.k.a. leaf
         if content is not None:
             gc = content if isinstance(content, StringTree) else StringTree('', content=content)
+            # Make sure no existing grand child is updated. It would reside too
+            # far up in the grand child OrderedDict, we need it last
+            if gc.content in self.children[nibble].children:
+                del self.children[nibble].children[gc.content]
             self.children[nibble].children[gc.content] = gc
         return self.children[nibble]