diff --git a/poincare/include/poincare/tree_handle.h b/poincare/include/poincare/tree_handle.h
index 68f99b41a..5e2a07d9b 100644
--- a/poincare/include/poincare/tree_handle.h
+++ b/poincare/include/poincare/tree_handle.h
@@ -128,7 +128,7 @@ protected:
   void setIdentifierAndRetain(uint16_t newId);
   void setTo(const TreeHandle & tr);
 
-  static bool hasNode(uint16_t identifier) { return identifier < TreeNode::NoNodeIdentifier; }
+  static bool hasNode(uint16_t identifier) { return TreeNode::IsValidIdentifier(identifier); }
 
   /* Hierarchy operations */
   // Add
diff --git a/poincare/include/poincare/tree_node.h b/poincare/include/poincare/tree_node.h
index f46d6ff9a..71d1df351 100644
--- a/poincare/include/poincare/tree_node.h
+++ b/poincare/include/poincare/tree_node.h
@@ -172,6 +172,8 @@ public:
   void log(std::ostream & stream, bool recursive = true);
 #endif
 
+  static bool IsValidIdentifier(uint16_t id) { return id < NoNodeIdentifier; }
+
 protected:
   TreeNode() :
     m_identifier(NoNodeIdentifier),
diff --git a/poincare/include/poincare/tree_pool.h b/poincare/include/poincare/tree_pool.h
index 463c41ec8..0da0d8f80 100644
--- a/poincare/include/poincare/tree_pool.h
+++ b/poincare/include/poincare/tree_pool.h
@@ -27,7 +27,7 @@ public:
 
   // Node
   TreeNode * node(uint16_t identifier) const {
-    assert(identifier >= 0 && identifier < MaxNumberOfNodes);
+    assert(TreeNode::IsValidIdentifier(identifier) && identifier < MaxNumberOfNodes);
     if (m_nodeForIdentifierOffset[identifier] != UINT16_MAX) {
       return const_cast<TreeNode *>(reinterpret_cast<const TreeNode *>(m_alignedBuffer + m_nodeForIdentifierOffset[identifier]));
     }
@@ -125,7 +125,7 @@ private:
       }
     }
     void push(uint16_t i) {
-      assert(m_currentIndex >= 0 && m_currentIndex < MaxNumberOfNodes);
+      assert(TreeNode::IsValidIdentifier(m_currentIndex) && m_currentIndex < MaxNumberOfNodes);
       m_availableIdentifiers[m_currentIndex++] = i;
     }
     uint16_t pop() {
diff --git a/poincare/src/tree_pool.cpp b/poincare/src/tree_pool.cpp
index 00895e05d..7ab75d0d7 100644
--- a/poincare/src/tree_pool.cpp
+++ b/poincare/src/tree_pool.cpp
@@ -14,7 +14,7 @@ namespace Poincare {
 TreePool * TreePool::SharedStaticPool = nullptr;
 
 void TreePool::freeIdentifier(uint16_t identifier) {
-  if (identifier >= 0 && identifier < MaxNumberOfNodes) {
+  if (TreeNode::IsValidIdentifier(identifier) && identifier < MaxNumberOfNodes) {
     m_nodeForIdentifierOffset[identifier] = UINT16_MAX;
     m_identifiers.push(identifier);
   }