diff --git a/butils.py b/butils.py
index 94ed804..2e22b05 100644
--- a/butils.py
+++ b/butils.py
@@ -820,11 +820,12 @@ def update_matrices(obj):
 def is_or_has_parent(o, parent, if_is_parent=True, max_depth=10):
     if o == parent and if_is_parent:
         return True
+    oo = o
     for i in range(0, max_depth):
-        o = o.parent
-        if o == parent:
+        oo = oo.parent
+        if oo == parent:
             return True
-        if o is None:
+        if oo is None:
             return False
     return False