diff --git a/poincare/include/poincare/allocation_failed_layout_node.h b/poincare/include/poincare/allocation_failed_layout_node.h
index b5fb6e5a6..1f4253bfc 100644
--- a/poincare/include/poincare/allocation_failed_layout_node.h
+++ b/poincare/include/poincare/allocation_failed_layout_node.h
@@ -22,6 +22,7 @@ public:
   // TreeNode
   size_t size() const override { return sizeof(AllocationFailedLayoutNode); }
   const char * description() const override { return "Allocation Failed";  }
+  int numberOfChildren() const override { return 0; }
   bool isAllocationFailure() const override { return true; }
 
 protected:
diff --git a/poincare/include/poincare/binomial_coefficient_layout_node.h b/poincare/include/poincare/binomial_coefficient_layout_node.h
index b01de28f7..ac2613bd2 100644
--- a/poincare/include/poincare/binomial_coefficient_layout_node.h
+++ b/poincare/include/poincare/binomial_coefficient_layout_node.h
@@ -23,6 +23,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(BinomialCoefficientLayoutNode); }
+  int numberOfChildren() const override { return 2; }
 #if TREE_LOG
   const char * description() const override {
     return "BinomialCoefficientLayout";
diff --git a/poincare/include/poincare/bracket_layout_node.h b/poincare/include/poincare/bracket_layout_node.h
index f8a032062..3b3272524 100644
--- a/poincare/include/poincare/bracket_layout_node.h
+++ b/poincare/include/poincare/bracket_layout_node.h
@@ -22,6 +22,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(BracketLayoutNode); }
+  int numberOfChildren() const override { return 0; }
 #if TREE_LOG
   const char * description() const override { return "BracketLayout"; }
 #endif
diff --git a/poincare/include/poincare/bracket_pair_layout_node.h b/poincare/include/poincare/bracket_pair_layout_node.h
index 193f8eebd..1c167e088 100644
--- a/poincare/include/poincare/bracket_pair_layout_node.h
+++ b/poincare/include/poincare/bracket_pair_layout_node.h
@@ -26,6 +26,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(BracketPairLayoutNode); }
+  int numberOfChildren() const override { return 1; }
 #if TREE_LOG
   const char * description() const override { return "BracketPairLayout"; }
 #endif
diff --git a/poincare/include/poincare/char_layout_node.h b/poincare/include/poincare/char_layout_node.h
index 93c1e4f6f..f57023d76 100644
--- a/poincare/include/poincare/char_layout_node.h
+++ b/poincare/include/poincare/char_layout_node.h
@@ -28,6 +28,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(CharLayoutNode); }
+  int numberOfChildren() const override { return 0; }
 #if TREE_LOG
   const char * description() const override {
     static char Description[] = "Char a";
diff --git a/poincare/include/poincare/condensed_sum_layout_node.h b/poincare/include/poincare/condensed_sum_layout_node.h
index 3e3fecb4b..76489bb5a 100644
--- a/poincare/include/poincare/condensed_sum_layout_node.h
+++ b/poincare/include/poincare/condensed_sum_layout_node.h
@@ -27,6 +27,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(CondensedSumLayoutNode); }
+  int numberOfChildren() const override { return 3; }
 #if TREE_LOG
   const char * description() const override {
     return "CondensedSumLayout";
diff --git a/poincare/include/poincare/conjugate_layout_node.h b/poincare/include/poincare/conjugate_layout_node.h
index e206f56e4..b95a33def 100644
--- a/poincare/include/poincare/conjugate_layout_node.h
+++ b/poincare/include/poincare/conjugate_layout_node.h
@@ -19,6 +19,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(ConjugateLayoutNode); }
+  int numberOfChildren() const override { return 1; }
 #if TREE_LOG
   const char * description() const override {
     return "ConjugateLayout";
diff --git a/poincare/include/poincare/empty_layout_node.h b/poincare/include/poincare/empty_layout_node.h
index 6de80aeb0..b0fc1937d 100644
--- a/poincare/include/poincare/empty_layout_node.h
+++ b/poincare/include/poincare/empty_layout_node.h
@@ -39,6 +39,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(EmptyLayoutNode); }
+  int numberOfChildren() const override { return 0; }
 #if TREE_LOG
   const char * description() const override { return "Empty"; }
 #endif
diff --git a/poincare/include/poincare/fraction_layout_node.h b/poincare/include/poincare/fraction_layout_node.h
index 4227d482e..87e0a5e82 100644
--- a/poincare/include/poincare/fraction_layout_node.h
+++ b/poincare/include/poincare/fraction_layout_node.h
@@ -33,6 +33,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(FractionLayoutNode); }
+  int numberOfChildren() const override { return 2; }
 #if TREE_LOG
   const char * description() const override {
     return "FractionLayout";
diff --git a/poincare/include/poincare/grid_layout_node.h b/poincare/include/poincare/grid_layout_node.h
index 792d5518a..b825d4450 100644
--- a/poincare/include/poincare/grid_layout_node.h
+++ b/poincare/include/poincare/grid_layout_node.h
@@ -19,6 +19,7 @@ class GridLayoutNode : public LayoutNode {
 public:
   GridLayoutNode() :
     LayoutNode(),
+    m_numberOfChildren(0),
     m_numberOfRows(0),
     m_numberOfColumns(0)
   {}
@@ -41,8 +42,20 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(GridLayoutNode); }
+  int numberOfChildren() const override { return m_numberOfChildren; }
+  void incrementNumberOfChildren(int increment = 1) override {
+    assert(increment >= 0);
+    m_numberOfChildren += increment;
+  }
+  void decrementNumberOfChildren(int decrement = 1) override {
+    m_numberOfChildren -= decrement;
+    if (m_numberOfChildren < 0) {
+      m_numberOfChildren = 0;
+    }
+  }
+
   void eraseNumberOfChildren() override {
-    LayoutNode::eraseNumberOfChildren();
+    m_numberOfChildren = 0;
     m_numberOfRows = 0;
     m_numberOfColumns = 0;
   }
@@ -65,6 +78,7 @@ protected:
   int rowAtChildIndex(int index) const;
   int columnAtChildIndex(int index) const;
   int indexAtRowColumn(int rowIndex, int columnIndex) const;
+  int m_numberOfChildren;
   int m_numberOfRows;
   int m_numberOfColumns;
 
diff --git a/poincare/include/poincare/horizontal_layout_node.h b/poincare/include/poincare/horizontal_layout_node.h
index 232caffa8..d26b2a2c1 100644
--- a/poincare/include/poincare/horizontal_layout_node.h
+++ b/poincare/include/poincare/horizontal_layout_node.h
@@ -13,7 +13,10 @@ namespace Poincare {
 class HorizontalLayoutNode : public LayoutNode {
   friend class LayoutReference;
 public:
-  using LayoutNode::LayoutNode;
+  HorizontalLayoutNode() :
+    LayoutNode(),
+    m_numberOfChildren(0)
+  {}
 
   // LayoutNode
   void moveCursorLeft(LayoutCursor * cursor, bool * shouldRecomputeLayout) override;
@@ -23,11 +26,18 @@ public:
   int writeTextInBuffer(char * buffer, int bufferSize, PrintFloat::Mode floatDisplayMode, int numberOfSignificantDigits) const override;
 
   bool isHorizontal() const override { return true; }
-  bool isEmpty() const override { return numberOfChildren() == 1 && const_cast<HorizontalLayoutNode *>(this)->childAtIndex(0)->isEmpty(); }
-  bool isCollapsable(int * numberOfOpenParenthesis, bool goingLeft) const override { return numberOfChildren() != 0; }
+  bool isEmpty() const override { return m_numberOfChildren == 1 && const_cast<HorizontalLayoutNode *>(this)->childAtIndex(0)->isEmpty(); }
+  bool isCollapsable(int * numberOfOpenParenthesis, bool goingLeft) const override { return m_numberOfChildren != 0; }
 
   // TreeNode
   size_t size() const override { return sizeof(HorizontalLayoutNode); }
+  int numberOfChildren() const override { return m_numberOfChildren; }
+  void incrementNumberOfChildren(int increment = 1) override { m_numberOfChildren+= increment; }
+  void decrementNumberOfChildren(int decrement = 1) override {
+    assert(m_numberOfChildren >= decrement);
+    m_numberOfChildren-= decrement;
+  }
+  void eraseNumberOfChildren() override { m_numberOfChildren = 0; }
 #if TREE_LOG
   const char * description() const override {
     return "Horizontal Layout";
@@ -47,6 +57,7 @@ private:
   void didRemoveChildAtIndex(int index, LayoutCursor * cursor, bool force) override;
   bool willReplaceChild(LayoutNode * oldChild, LayoutNode * newChild, LayoutCursor * cursor, bool force) override;
   void render(KDContext * ctx, KDPoint p, KDColor expressionColor, KDColor backgroundColor) override {}
+  int m_numberOfChildren;
 };
 
 class HorizontalLayoutRef : public LayoutReference {
diff --git a/poincare/include/poincare/integral_layout_node.h b/poincare/include/poincare/integral_layout_node.h
index cda5e46f0..0ebb572f4 100644
--- a/poincare/include/poincare/integral_layout_node.h
+++ b/poincare/include/poincare/integral_layout_node.h
@@ -30,6 +30,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(IntegralLayoutNode); }
+  int numberOfChildren() const override { return 3; }
 #if TREE_LOG
   const char * description() const override {
     return "IntegralLayout";
diff --git a/poincare/include/poincare/nth_root_layout_node.h b/poincare/include/poincare/nth_root_layout_node.h
index 6292fc40d..709d45ab0 100644
--- a/poincare/include/poincare/nth_root_layout_node.h
+++ b/poincare/include/poincare/nth_root_layout_node.h
@@ -12,7 +12,10 @@ public:
   constexpr static KDCoordinate k_leftRadixHeight = 8;
   constexpr static KDCoordinate k_leftRadixWidth = 5;
 
-  using LayoutNode::LayoutNode;
+  NthRootLayoutNode() :
+    LayoutNode(),
+    m_numberOfChildren(0)
+  {}
 
   // LayoutNode
   void moveCursorLeft(LayoutCursor * cursor, bool * shouldRecomputeLayout) override;
@@ -25,7 +28,16 @@ public:
   bool hasUpperLeftIndex() const override { return numberOfChildren() > 1; }
 
   // TreeNode
+  void incrementNumberOfChildren(int increment = 1) override {
+    assert(increment == 1);
+    m_numberOfChildren+= increment;
+  }
+  void decrementNumberOfChildren(int decrement = 1) override {
+    assert(m_numberOfChildren >= decrement);
+    m_numberOfChildren-= decrement;
+  }
   size_t size() const override { return sizeof(NthRootLayoutNode); }
+  int numberOfChildren() const override { return m_numberOfChildren; }
 #if TREE_LOG
   const char * description() const override {
     return "NthRootLayout";
@@ -54,6 +66,7 @@ private:
     assert(numberOfChildren() == 1 || numberOfChildren() == 2);
     return numberOfChildren() == 2 ? childAtIndex(1) : nullptr;
   }
+  int m_numberOfChildren;
 };
 
 class NthRootLayoutRef : public LayoutReference {
diff --git a/poincare/include/poincare/sequence_layout_node.h b/poincare/include/poincare/sequence_layout_node.h
index 36b6b8bbc..73700e8d2 100644
--- a/poincare/include/poincare/sequence_layout_node.h
+++ b/poincare/include/poincare/sequence_layout_node.h
@@ -28,6 +28,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(SequenceLayoutNode); }
+  int numberOfChildren() const override { return 3; }
 #if TREE_LOG
   const char * description() const override {
     return "Sequence Layout";
diff --git a/poincare/include/poincare/tree_node.h b/poincare/include/poincare/tree_node.h
index 2dddfe725..784757056 100644
--- a/poincare/include/poincare/tree_node.h
+++ b/poincare/include/poincare/tree_node.h
@@ -53,12 +53,10 @@ public:
   // Hierarchy
   TreeNode * parent() const;
   TreeNode * root();
-  int numberOfChildren() const { return m_numberOfChildren; }
-  void incrementNumberOfChildren(int increment = 1) { m_numberOfChildren += increment; }
-  void decrementNumberOfChildren(int decrement = 1) {
-    m_numberOfChildren = m_numberOfChildren > decrement ? m_numberOfChildren - decrement : 0;
-  }
-  virtual void eraseNumberOfChildren() { m_numberOfChildren = 0; }
+  virtual int numberOfChildren() const = 0;
+  virtual void incrementNumberOfChildren(int increment = 1) {} // Do no put an assert(false), we need this method for instance in GridLayout::removeRow
+  virtual void decrementNumberOfChildren(int decrement = 1) {} // Do no put an assert(false), we need this method for instance in GridLayout::removeRow
+  virtual void eraseNumberOfChildren() {} //TODO Put an assert false //TODO what if somebody i stealing a unary tree's only child ?
   int numberOfDescendants(bool includeSelf) const;
   TreeNode * childAtIndex(int i) const;
   int indexOfChildByIdentifier(int childID) const;
@@ -175,7 +173,6 @@ protected:
 private:
   int m_identifier;
   int m_referenceCounter;
-  int m_numberOfChildren;
 };
 
 }
diff --git a/poincare/include/poincare/vertical_offset_layout_node.h b/poincare/include/poincare/vertical_offset_layout_node.h
index 5040bd96d..ed7bed12d 100644
--- a/poincare/include/poincare/vertical_offset_layout_node.h
+++ b/poincare/include/poincare/vertical_offset_layout_node.h
@@ -35,6 +35,7 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(VerticalOffsetLayoutNode); }
+  int numberOfChildren() const override { return 1; }
 #if TREE_LOG
   const char * description() const override {
     return m_type == Type::Subscript ? "Subscript" : "Superscript";
diff --git a/poincare/src/horizontal_layout_node.cpp b/poincare/src/horizontal_layout_node.cpp
index e94cf6525..7856f70ed 100644
--- a/poincare/src/horizontal_layout_node.cpp
+++ b/poincare/src/horizontal_layout_node.cpp
@@ -217,7 +217,7 @@ KDPoint HorizontalLayoutNode::positionOfChild(LayoutNode * l) {
 // Private
 
 bool HorizontalLayoutNode::willAddChildAtIndex(LayoutNode * l, int * index, LayoutCursor * cursor) {
-  if (numberOfChildren() > 0) {
+  if (m_numberOfChildren > 0) {
     *index = HorizontalLayoutRef(this).removeEmptyChildBeforeInsertionAtIndex(*index, !childAtIndex(0)->mustHaveLeftSibling(), cursor);
 
   }