diff --git a/poincare/include/poincare/tree_handle.h b/poincare/include/poincare/tree_handle.h
index f9e58440b..87b6ade6d 100644
--- a/poincare/include/poincare/tree_handle.h
+++ b/poincare/include/poincare/tree_handle.h
@@ -107,6 +107,8 @@ protected:
   void setIdentifierAndRetain(int newId);
   void setTo(const TreeHandle & tr);
 
+  static bool hasNode(int identifier) { return identifier > TreeNode::NoNodeIdentifier; }
+
   /* Hierarchy operations */
   // Add
   void addChildAtIndexInPlace(TreeHandle t, int index, int currentNumberOfChildren);
diff --git a/poincare/src/tree_handle.cpp b/poincare/src/tree_handle.cpp
index e4eaba5ed..1ae1abe60 100644
--- a/poincare/src/tree_handle.cpp
+++ b/poincare/src/tree_handle.cpp
@@ -16,7 +16,7 @@ TreeHandle TreeHandle::clone() const {
 }
 
 /* Hierarchy operations */
-TreeNode * TreeHandle::node() const { assert(m_identifier != TreeNode::NoNodeIdentifier); return TreePool::sharedPool()->node(m_identifier); }
+TreeNode * TreeHandle::node() const { assert(hasNode(m_identifier)); return TreePool::sharedPool()->node(m_identifier); }
 
 size_t TreeHandle::size() const { return node()->deepSize(node()->numberOfChildren()); }
 
@@ -204,7 +204,7 @@ void TreeHandle::setTo(const TreeHandle & tr) {
 }
 
 void TreeHandle::release(int identifier) {
-  if (identifier == TreeNode::NoNodeIdentifier) {
+  if (!hasNode(identifier)) {
     return;
   }
   TreeNode * node = TreePool::sharedPool()->node(identifier);
diff --git a/poincare/src/tree_node.cpp b/poincare/src/tree_node.cpp
index 1c8df84ee..3036690b6 100644
--- a/poincare/src/tree_node.cpp
+++ b/poincare/src/tree_node.cpp
@@ -31,7 +31,7 @@ void TreeNode::rename(int identifier, bool unregisterPreviousIdentifier) {
 // Hierarchy
 
 TreeNode * TreeNode::parent() const {
-  return m_parentIdentifier == NoNodeIdentifier ? nullptr : TreePool::sharedPool()->node(m_parentIdentifier);
+  return TreeHandle::hasNode(m_parentIdentifier) ?  TreePool::sharedPool()->node(m_parentIdentifier) : nullptr;
 }
 
 TreeNode * TreeNode::root() {