diff --git a/poincare/include/poincare/parenthesis.h b/poincare/include/poincare/parenthesis.h
index 0dec079eb..c6e17edae 100644
--- a/poincare/include/poincare/parenthesis.h
+++ b/poincare/include/poincare/parenthesis.h
@@ -26,7 +26,7 @@ public:
   LayoutRef createLayout(Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
   int serialize(char * buffer, int bufferSize, Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const override;
   // Simplification
-  Expression shallowReduce(Context& context, Preferences::AngleUnit angleUnit) override;
+  Expression shallowReduce(Context& context, Preferences::AngleUnit angleUnit) const override;
 
   // Approximation
   Evaluation<float> approximate(SinglePrecision p, Context& context, Preferences::AngleUnit angleUnit) const override { return templatedApproximate<float>(context, angleUnit); }
@@ -35,9 +35,10 @@ private:
  template<typename T> Evaluation<T> templatedApproximate(Context& context, Preferences::AngleUnit angleUnit) const;
 };
 
-class ParenthesisReference : public Expression {
+class Parenthesis : public Expression {
 public:
-  ParenthesisReference(Expression exp) : Expression(TreePool::sharedPool()->createTreeNode<ParenthesisNode>()) {
+  Parenthesis(const ParenthesisNode * n) : Expression(n) {}
+  Parenthesis(Expression exp) : Expression(TreePool::sharedPool()->createTreeNode<ParenthesisNode>()) {
     replaceChildAtIndexInPlace(0, exp);
   }
   // Expression
diff --git a/poincare/src/parenthesis.cpp b/poincare/src/parenthesis.cpp
index 9e3fa338e..0053d9100 100644
--- a/poincare/src/parenthesis.cpp
+++ b/poincare/src/parenthesis.cpp
@@ -1,6 +1,6 @@
 #include <poincare/parenthesis.h>
 #include <poincare/allocation_failure_expression_node.h>
-#include <assert.h>
+#include <poincare/serialization_helper.h>
 
 namespace Poincare {
 
@@ -18,7 +18,7 @@ LayoutRef ParenthesisNode::createLayout(Preferences::PrintFloatMode floatDisplay
 }
 
 int ParenthesisNode::serialize(char * buffer, int bufferSize, Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const {
-  return SerializationHelper::Prefix(Parenthesis(const_cast<ParenthesisNode *>(this)), buffer, bufferSize, floatDisplayMode, numberOfSignificantDigits, "");
+  return SerializationHelper::Prefix(this, buffer, bufferSize, floatDisplayMode, numberOfSignificantDigits, "");
 }
 
 Expression ParenthesisNode::shallowReduce(Context& context, Preferences::AngleUnit angleUnit) const {
@@ -32,7 +32,7 @@ Evaluation<T> ParenthesisNode::templatedApproximate(Context& context, Preference
 
 Expression Parenthesis::shallowReduce(Context& context, Preferences::AngleUnit angleUnit) const {
   Expression e = Expression::shallowReduce(context, angleUnit);
-  if (e != *this) {
+  if (e.isUndefinedOrAllocationFailure()) {
     return e;
   }
   return childAtIndex(0);