diff --git a/poincare/src/addition.cpp b/poincare/src/addition.cpp
index bb19995a0..72b7bc522 100644
--- a/poincare/src/addition.cpp
+++ b/poincare/src/addition.cpp
@@ -39,7 +39,7 @@ void Addition::immediateSimplify() {
   }
   sortChildren();
   int i = 0;
-  while (i < numberOfOperands()-1) {
+  while (i < numberOfOperands()) {
     if (deleteUselessOperand(i) && i > 0) {
       i--;
     }
diff --git a/poincare/src/dynamic_hierarchy.cpp b/poincare/src/dynamic_hierarchy.cpp
index 5e97b5f38..eaf59efd1 100644
--- a/poincare/src/dynamic_hierarchy.cpp
+++ b/poincare/src/dynamic_hierarchy.cpp
@@ -159,8 +159,8 @@ void DynamicHierarchy::squashUnaryHierarchy() {
 }
 
 bool DynamicHierarchy::deleteUselessOperand(int index) {
-  assert(index < numberOfOperands() && numberOfOperands() > 1);
-  if (operand(index)->type() == Type::Rational && isUselessOperand(static_cast<const Rational *>(operand(index)))) {
+  assert(index < numberOfOperands());
+  if (numberOfOperands() >1 && operand(index)->type() == Type::Rational && isUselessOperand(static_cast<const Rational *>(operand(index)))) {
     removeOperand(operand(index), true);
     return true;
   }
diff --git a/poincare/src/multiplication.cpp b/poincare/src/multiplication.cpp
index b7f544cc7..7b5a3efa8 100644
--- a/poincare/src/multiplication.cpp
+++ b/poincare/src/multiplication.cpp
@@ -113,7 +113,7 @@ void Multiplication::immediateSimplify() {
   sortChildren();
   /* Now, no more node can be an addition or a multiplication */
   int i = 0;
-  while (i < numberOfOperands()-1) {
+  while (i < numberOfOperands()) {
     if (deleteUselessOperand(i) && i > 0) {
       i--;
     }
diff --git a/poincare/test/simplify_easy.cpp b/poincare/test/simplify_easy.cpp
index 795de0161..c1f4e7ef8 100644
--- a/poincare/test/simplify_easy.cpp
+++ b/poincare/test/simplify_easy.cpp
@@ -120,6 +120,7 @@ QUIZ_CASE(poincare_simplify_easy) {
   assert_parsed_expression_simplify_to("A^3*A^(-3)", "1");
   assert_parsed_expression_simplify_to("1+A+2+B+3", "6+A+B");
   assert_parsed_expression_simplify_to("(x+1)*(x+2)", "x^2+3x+2");
+  assert_parsed_expression_simplify_to("(x+1)*(x-1)", "-1+x^2");
   /* This does not work but should not as it is above k_primorial32 = 1*3*5*7*11*... (product of first 32 primes. */
   //assert_parsed_expression_simplify_to("1881676377434183981909562699940347954480361860897069^(1/3)", "123456789123456789");