diff --git a/mapytex/calculus/core/renders/tree2tex.py b/mapytex/calculus/core/renders/tree2tex.py
index 3b24f18..d64abdd 100644
--- a/mapytex/calculus/core/renders/tree2tex.py
+++ b/mapytex/calculus/core/renders/tree2tex.py
@@ -197,9 +197,9 @@ def render_with_parenthesis(subtree, operator):
         except (AttributeError, KeyError):
             pass
         try:
-            subtree_ = subtree.__txt__
+            subtree_ = subtree.__tex__
         except AttributeError:
-            subtree_ = subtree
+            subtree_ = str(subtree)
     else:
         if OPERATORS[subtree.node]["precedence"] < OPERATORS[operator]["precedence"]:
             subtree_need_parenthesis = True
diff --git a/mapytex/calculus/core/renders/tree2txt.py b/mapytex/calculus/core/renders/tree2txt.py
index d6c36c3..826ee0d 100644
--- a/mapytex/calculus/core/renders/tree2txt.py
+++ b/mapytex/calculus/core/renders/tree2txt.py
@@ -203,7 +203,7 @@ def render_with_parenthesis(subtree, operator):
         try:
             subtree_ = subtree.__txt__
         except AttributeError:
-            subtree_ = subtree
+            subtree_ = str(subtree)
     else:
         if OPERATORS[subtree.node]["precedence"] < OPERATORS[operator]["precedence"]:
             subtree_need_parenthesis = True