diff --git a/docs/changelog.md b/docs/changelog.md
index cc31289d..f20687c0 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -15,6 +15,7 @@ See the [Contributing Guide](contributing.md) for details.
 ## [Unreleased]
 
 * Update serializer to be non-recursive (#1644).
+* Improve ancestor handling in the inline `Treeprocessor` (#1646).
 
 ## [3.11.0] - 2026-09-25
 
diff --git a/markdown/treeprocessors.py b/markdown/treeprocessors.py
index 4d2f318d..a148175f 100644
--- a/markdown/treeprocessors.py
+++ b/markdown/treeprocessors.py
@@ -371,12 +371,14 @@ def run(self, tree: etree.Element, ancestors: list[str] | None = None) -> etree.
 
         self.parent_map = {c: p for p in tree.iter() for c in p}
         stack = [(tree, tree_parents)]
+        self.__build_ancestors(tree, tree_parents)
 
         while stack:
             currElement, parents = stack.pop(0)
 
             self.ancestors = parents
-            self.__build_ancestors(currElement, self.ancestors)
+            if currElement is not tree:
+                self.ancestors.append(currElement.tag.lower())
 
             insertQueue = []
             for child in currElement: