diff --git a/poincare/include/poincare/horizontal_layout_node.h b/poincare/include/poincare/horizontal_layout_node.h
index b11907a54..4f4542874 100644
--- a/poincare/include/poincare/horizontal_layout_node.h
+++ b/poincare/include/poincare/horizontal_layout_node.h
@@ -44,6 +44,7 @@ public:
     m_numberOfChildren-= decrement;
   }
   void eraseNumberOfChildren() override { m_numberOfChildren = 0; }
+  void childAtIndexWillBeStolen(int index) override;
 #if POINCARE_TREE_LOG
   virtual void logNodeName(std::ostream & stream) const override {
     stream << "HorizontalLayout";
diff --git a/poincare/include/poincare/n_ary_expression_node.h b/poincare/include/poincare/n_ary_expression_node.h
index 0cb8df62b..bb9f2ad3f 100644
--- a/poincare/include/poincare/n_ary_expression_node.h
+++ b/poincare/include/poincare/n_ary_expression_node.h
@@ -17,6 +17,7 @@ public:
     m_numberOfChildren-= decrement;
   }
   void eraseNumberOfChildren() override { m_numberOfChildren = 0; }
+  void childAtIndexWillBeStolen(int index) override;
 
   // Comparison
   typedef int (*ExpressionOrder)(const ExpressionNode * e1, const ExpressionNode * e2, bool canBeInterrupted);
diff --git a/poincare/include/poincare/tree_by_reference.h b/poincare/include/poincare/tree_by_reference.h
index aeb21270d..a3c8822fd 100644
--- a/poincare/include/poincare/tree_by_reference.h
+++ b/poincare/include/poincare/tree_by_reference.h
@@ -83,6 +83,9 @@ public:
   int indexOfChild(TreeByReference t) const {
     return node()->indexOfChild(t.node());
   }
+  void childAtIndexWillBeStolen(int index) {
+    node()->childAtIndexWillBeStolen(index);
+  }
 
   /* Hierarchy operations */
   // Replace
@@ -90,6 +93,10 @@ public:
   void replaceChildInPlace(TreeByReference oldChild, TreeByReference newChild);
   void replaceChildAtIndexInPlace(int oldChildIndex, TreeByReference newChild);
   void replaceWithAllocationFailureInPlace(int currentNumberOfChildren);
+  void replaceChildAtIndexWithGhostInPlace(int index) {
+    assert(index >= 0 && index < numberOfChildren());
+    replaceChildWithGhostInPlace(childAtIndex(index));
+  }
   void replaceChildWithGhostInPlace(TreeByReference t);
   // Merge
   void mergeChildrenAtIndexInPlace(TreeByReference t, int i);
@@ -124,6 +131,7 @@ protected:
   int m_identifier;
 
 private:
+  void detachFromParent();
   // Add ghost children on layout construction
   void buildGhostChildren();
 };
diff --git a/poincare/include/poincare/tree_node.h b/poincare/include/poincare/tree_node.h
index fb0c33ec3..202d453e1 100644
--- a/poincare/include/poincare/tree_node.h
+++ b/poincare/include/poincare/tree_node.h
@@ -69,6 +69,8 @@ public:
   bool hasChild(const TreeNode * child) const;
   bool hasAncestor(const TreeNode * node, bool includeSelf) const;
   bool hasSibling(const TreeNode * e) const;
+  // Prepare a child that will be stolen by another Expression
+  virtual void childAtIndexWillBeStolen(int index);
   // AddChild collateral effect
   virtual void didAddChildAtIndex(int newNumberOfChildren) {}
 
diff --git a/poincare/src/horizontal_layout_node.cpp b/poincare/src/horizontal_layout_node.cpp
index 56c91220d..3ee9373c2 100644
--- a/poincare/src/horizontal_layout_node.cpp
+++ b/poincare/src/horizontal_layout_node.cpp
@@ -193,6 +193,10 @@ bool HorizontalLayoutNode::hasText() const {
   return true;
 }
 
+void HorizontalLayoutNode::childAtIndexWillBeStolen(int index) {
+  HorizontalLayoutRef(this).removeChildAtIndex(index, nullptr);
+}
+
 // Protected
 
 KDSize HorizontalLayoutNode::computeSize() {
diff --git a/poincare/src/n_ary_expression_node.cpp b/poincare/src/n_ary_expression_node.cpp
index 3f3889512..c788494ad 100644
--- a/poincare/src/n_ary_expression_node.cpp
+++ b/poincare/src/n_ary_expression_node.cpp
@@ -36,6 +36,10 @@ Expression NAryExpressionNode::squashUnaryHierarchy() {
   return copy;
 }
 
+void NAryExpressionNode::childAtIndexWillBeStolen(int index) {
+  NAryExpression(this).removeChildAtIndexInPlace(index);
+}
+
 // Private
 
 int NAryExpressionNode::simplificationOrderSameType(const ExpressionNode * e, bool canBeInterrupted) const {
diff --git a/poincare/src/tree_by_reference.cpp b/poincare/src/tree_by_reference.cpp
index 09761d0a4..8232932db 100644
--- a/poincare/src/tree_by_reference.cpp
+++ b/poincare/src/tree_by_reference.cpp
@@ -68,6 +68,9 @@ void TreeByReference::replaceChildInPlace(TreeByReference oldChild, TreeByRefere
     return;
   }
 
+  // If the new child has a parent, detach from it
+  newChild.detachFromParent();
+
   // Move the new child
   assert(newChild.isGhost() || newChild.parent().isUninitialized());
   TreePool::sharedPool()->move(oldChild.node(), newChild.node(), newChild.numberOfChildren());
@@ -144,6 +147,10 @@ void TreeByReference::replaceChildWithGhostInPlace(TreeByReference t) {
 }
 
 void TreeByReference::mergeChildrenAtIndexInPlace(TreeByReference t, int i) {
+  /* mergeChildrenAtIndexInPlace should only be called with a tree thant can
+   * have any number of children, so there is no need to replace the stolen
+   * children with ghosts. */
+  // TODO assert this and t are "dynamic" trees
   assert(i >= 0 && i <= numberOfChildren());
   // Steal operands
   int numberOfNewChildren = t.numberOfChildren();
@@ -196,8 +203,8 @@ void TreeByReference::addChildAtIndexInPlace(TreeByReference t, int index, int c
     replaceWithAllocationFailureInPlace(currentNumberOfChildren);
     return;
   }
+
   assert(index >= 0 && index <= currentNumberOfChildren);
-  assert(t.parent().isUninitialized());
 
   // If the new node is static, copy it in the pool and add the copy
   if (t.isStatic()) {
@@ -210,6 +217,10 @@ void TreeByReference::addChildAtIndexInPlace(TreeByReference t, int index, int c
     return;
   }
 
+  // If t has a parent, detach t from it.
+  t.detachFromParent();
+  assert(t.parent().isUninitialized());
+
   // Move t
   TreeNode * newChildPosition = node()->next();
   for (int i = 0; i < index; i++) {
@@ -251,6 +262,15 @@ void TreeByReference::removeChildrenInPlace(int currentNumberOfChildren) {
 
 /* Private */
 
+void TreeByReference::detachFromParent() {
+  TreeByReference myParent = parent();
+  if (!myParent.isUninitialized()) {
+    int idxInParent = myParent.indexOfChild(*this);
+    myParent.childAtIndexWillBeStolen(idxInParent);
+  }
+  assert(parent().isUninitialized());
+}
+
 void TreeByReference::setTo(const TreeByReference & tr) {
   /* We cannot use (*this)==tr because tr would need to be casted to
    * TreeByReference, which calls setTo and triggers an infinite loop */
diff --git a/poincare/src/tree_node.cpp b/poincare/src/tree_node.cpp
index 16d0ec1b9..80a1922c4 100644
--- a/poincare/src/tree_node.cpp
+++ b/poincare/src/tree_node.cpp
@@ -192,6 +192,10 @@ TreeNode * TreeNode::nextSibling() const {
   return node;
 }
 
+void TreeNode::childAtIndexWillBeStolen(int index) {
+  TreeByReference(this).replaceChildAtIndexWithGhostInPlace(index);
+}
+
 TreeNode * TreeNode::lastDescendant() const {
   TreeNode * node = const_cast<TreeNode *>(this);
   int remainingNodesToVisit = node->numberOfChildren();