diff --git a/poincare/include/poincare/serialization_helper.h b/poincare/include/poincare/serialization_helper.h
index a68f5389e..ac38a895f 100644
--- a/poincare/include/poincare/serialization_helper.h
+++ b/poincare/include/poincare/serialization_helper.h
@@ -34,6 +34,14 @@ namespace SerializationHelper {
       int firstChildIndex = 0,
       int lastChildIndex = -1);
 
+  int SerializeChild(
+    const TreeNode * childNode,
+    const TreeNode * parentNode,
+    char * buffer,
+    int bufferSize,
+    Preferences::PrintFloatMode floatDisplayMode,
+    int numberOfDigits);
+
   // Write one code point in a buffer and a null-terminating char
   int CodePoint(char * buffer, int bufferSize, CodePoint c);
 };
diff --git a/poincare/src/factorial.cpp b/poincare/src/factorial.cpp
index c39f262cd..402b54bd8 100644
--- a/poincare/src/factorial.cpp
+++ b/poincare/src/factorial.cpp
@@ -67,21 +67,8 @@ Layout FactorialNode::createLayout(Preferences::PrintFloatMode floatDisplayMode,
 }
 
 int FactorialNode::serialize(char * buffer, int bufferSize, Preferences::PrintFloatMode floatDisplayMode, int numberOfSignificantDigits) const {
-  if (bufferSize == 0) {
-    return -1;
-  }
-  buffer[bufferSize-1] = 0;
-  int numberOfChar = 0;
-  if (childNeedsParenthesis(childAtIndex(0))) {
-    numberOfChar += SerializationHelper::CodePoint(&buffer[numberOfChar], bufferSize-numberOfChar, '(');
-    if (numberOfChar >= bufferSize-1) { return bufferSize-1; }
-  }
-  numberOfChar += childAtIndex(0)->serialize(buffer+numberOfChar, bufferSize-numberOfChar, floatDisplayMode, numberOfSignificantDigits);
-  if (childNeedsParenthesis(childAtIndex(0))) {
-    numberOfChar += SerializationHelper::CodePoint(&buffer[numberOfChar], bufferSize-numberOfChar, ')');
-    if (numberOfChar >= bufferSize-1) { return bufferSize-1; }
-  }
-  if (numberOfChar >= bufferSize-1) {
+  int numberOfChar = SerializationHelper::SerializeChild(childAtIndex(0), this, buffer, bufferSize, floatDisplayMode, numberOfSignificantDigits);
+  if ((numberOfChar < 0) || (numberOfChar >= bufferSize-1)) {
     return numberOfChar;
   }
   numberOfChar += SerializationHelper::CodePoint(&buffer[numberOfChar], bufferSize-numberOfChar, '!');
diff --git a/poincare/src/serialization_helper.cpp b/poincare/src/serialization_helper.cpp
index 595888df5..2f9b1f773 100644
--- a/poincare/src/serialization_helper.cpp
+++ b/poincare/src/serialization_helper.cpp
@@ -20,7 +20,7 @@ static bool checkBufferSize(char * buffer, int bufferSize, int * result) {
   return false;
 }
 
-static int serializeChild(
+int SerializationHelper::SerializeChild(
     const TreeNode * childNode,
     const TreeNode * parentNode,
     char * buffer,
@@ -83,7 +83,7 @@ int SerializationHelper::Infix(
   assert(numberOfChildren > 0);
 
   // Write the first child, with parentheses if needed
-  numberOfChar+= serializeChild(node->childAtIndex(firstChildIndex), node, buffer + numberOfChar, bufferSize - numberOfChar, floatDisplayMode, numberOfDigits);
+  numberOfChar+= SerializeChild(node->childAtIndex(firstChildIndex), node, buffer + numberOfChar, bufferSize - numberOfChar, floatDisplayMode, numberOfDigits);
   if (numberOfChar >= bufferSize-1) {
     assert(buffer[bufferSize - 1] == 0);
     return bufferSize-1;
@@ -98,7 +98,7 @@ int SerializationHelper::Infix(
       return bufferSize-1;
     }
     // Write the child, with parentheses if needed
-    numberOfChar+= serializeChild(node->childAtIndex(i), node, buffer + numberOfChar, bufferSize - numberOfChar, floatDisplayMode, numberOfDigits);
+    numberOfChar+= SerializeChild(node->childAtIndex(i), node, buffer + numberOfChar, bufferSize - numberOfChar, floatDisplayMode, numberOfDigits);
     if (numberOfChar >= bufferSize-1) {
       assert(buffer[bufferSize - 1] == 0);
       return bufferSize-1;