diff --git a/masque/library.py b/masque/library.py
index 9afd150..c69831e 100644
--- a/masque/library.py
+++ b/masque/library.py
@@ -1045,7 +1045,7 @@ class Tree(MutableLibrary):
             top: str,
             library: MutableLibrary | None = None
             ) -> None:
-        self.top = top if isinstance(top, str) else top.name
+        self.top = top
         self.library = library if library is not None else WrapLibrary()
 
     @classmethod