diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index a35894c5b..664ce6a64 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -29,7 +29,7 @@ class Expression {
 
     /* identicalTo means strictly the same tree. For example, 3+5 is NOT identi-
      * cal to 5+3. Those are equal, but not identical. */
-    //virtual bool identicalTo(Expression * e);
+    bool isIdenticalTo(Expression * e);
     Expression * simplify();
 
     virtual Type type() = 0;
diff --git a/poincare/src/expression.cpp b/poincare/src/expression.cpp
index 10b9e5e0a..53cb3d67a 100644
--- a/poincare/src/expression.cpp
+++ b/poincare/src/expression.cpp
@@ -43,3 +43,14 @@ Expression * Expression::simplify() {
   return result;
 }
 
+bool Expression::isIdenticalTo(Expression * e) {
+  if (e->type() != this->type() || e->numberOfOperands() != this->numberOfOperands()) {
+    return false;
+  }
+  for (int i=0; i<this->numberOfOperands(); i++) {
+    if (!e->operand(i)->isIdenticalTo(this->operand(i))) {
+      return false;
+    }
+  }
+  return true;
+}