diff --git a/poincare/include/poincare/serialization_helper.h b/poincare/include/poincare/serialization_helper.h
index e0ed71193..061e587ce 100644
--- a/poincare/include/poincare/serialization_helper.h
+++ b/poincare/include/poincare/serialization_helper.h
@@ -6,6 +6,12 @@
 
 namespace Poincare {
 
+/* The serialization methods write their argument as a string in the given
+ * buffer, with a null-terminating 0. The return value is:
+ *   -> -1 if the buffer size is 0
+ *   -> Otherwise, the number of chars written, without the null terminating 0
+ */
+
 namespace SerializationHelper {
   // SerializableReference to text
   int Infix(
@@ -30,7 +36,6 @@ namespace SerializationHelper {
   // Write one char in a buffer
   int Char(char * buffer, int bufferSize, char c);
   // Write one code point in a buffer
-  constexpr int MaxSerializedCodePointSize = CodePoint::MaxCodePointCharLength + 1; // Null-terminating char
   int CodePoint(char * buffer, int bufferSize, CodePoint c);
 };
 
diff --git a/poincare/src/constant.cpp b/poincare/src/constant.cpp
index 788cf5135..329babeda 100644
--- a/poincare/src/constant.cpp
+++ b/poincare/src/constant.cpp
@@ -93,7 +93,7 @@ bool ConstantNode::isConstantCodePoint(CodePoint c) const {
 }
 
 Constant Constant::Builder(CodePoint c) {
-  constexpr int bufferSize = SerializationHelper::MaxSerializedCodePointSize;
+  constexpr int bufferSize = CodePoint::MaxCodePointCharLength + 1;
   char buffer[bufferSize];
   size_t codePointSize = SerializationHelper::CodePoint(buffer, bufferSize, c);
   return SymbolAbstract::Builder<Constant, ConstantNode>(buffer, codePointSize);
diff --git a/poincare/src/serialization_helper.cpp b/poincare/src/serialization_helper.cpp
index 71cb9dc39..f77ddd247 100644
--- a/poincare/src/serialization_helper.cpp
+++ b/poincare/src/serialization_helper.cpp
@@ -5,24 +5,57 @@
 
 namespace Poincare {
 
-static void serializeChild(const TreeNode * childNode, const TreeNode * parentNode, char * buffer, int bufferSize, Preferences::PrintFloatMode floatDisplayMode, int numberOfDigits, int * numberOfChar) {
+static inline int min(int x, int y) { return x < y ? x : y; }
+
+static bool checkBufferSize(char * buffer, int bufferSize, int * result) {
+  // If buffer has size 0 or 1, put a zero if it fits and return
+  if (bufferSize == 0) {
+    *result = -1;
+    return true;
+  }
+
+  buffer[bufferSize-1] = 0; // Null-terminate the buffer
+  if (bufferSize == 1) {
+    *result = 0;
+    return true;
+  }
+  return false;
+}
+
+static int serializeChild(
+    const TreeNode * childNode,
+    const TreeNode * parentNode,
+    char * buffer,
+    int bufferSize,
+    Preferences::PrintFloatMode floatDisplayMode,
+    int numberOfDigits)
+{
+  {
+    int result = 0;
+    if (checkBufferSize(buffer, bufferSize, &result)) {
+      return result;
+    }
+  }
+
+  int numberOfChar = 0;
   // Write the child with parentheses if needed
   bool addParentheses = parentNode->childNeedsParenthesis(childNode);
   if (addParentheses) {
-    buffer[*numberOfChar] = '(';
-    *numberOfChar = *numberOfChar + 1;
-    if (*numberOfChar >= bufferSize-1) {
-      return;
+    buffer[numberOfChar++] = '(';
+    if (numberOfChar >= bufferSize-1) {
+      return bufferSize-1;
     }
   }
-  *numberOfChar += childNode->serialize(buffer + *numberOfChar, bufferSize - *numberOfChar, floatDisplayMode, numberOfDigits);
-  if (*numberOfChar >= bufferSize-1) {
-    return;
+  numberOfChar+= childNode->serialize(buffer + numberOfChar, bufferSize - numberOfChar, floatDisplayMode, numberOfDigits);
+  if (numberOfChar >= bufferSize-1) {
+    assert(buffer[bufferSize - 1] == 0);
+    return bufferSize-1;
   }
   if (addParentheses) {
-    buffer[*numberOfChar] = ')';
-    *numberOfChar = *numberOfChar + 1;
+    buffer[numberOfChar++] = ')';
   }
+  buffer[numberOfChar] = 0;
+  return numberOfChar;
 }
 
 int SerializationHelper::Infix(
@@ -35,14 +68,11 @@ int SerializationHelper::Infix(
     int firstChildIndex,
     int lastChildIndex)
 {
-  // If buffer has size 0 or 1, put a zero if it fits and return
-  if (bufferSize == 0) {
-    return -1;
-  }
-
-  buffer[bufferSize-1] = 0; // Null-terminate the buffer
-  if (bufferSize == 1) {
-    return 0;
+  {
+    int result = 0;
+    if (checkBufferSize(buffer, bufferSize, &result)) {
+      return result;
+    }
   }
 
   // Get some information on the node
@@ -51,8 +81,9 @@ int SerializationHelper::Infix(
   assert(numberOfChildren > 0);
 
   // Write the first child, with parentheses if needed
-  serializeChild(node->childAtIndex(firstChildIndex), node, buffer, bufferSize, floatDisplayMode, numberOfDigits, &numberOfChar);
+  numberOfChar+= serializeChild(node->childAtIndex(firstChildIndex), node, buffer + numberOfChar, bufferSize - numberOfChar, floatDisplayMode, numberOfDigits);
   if (numberOfChar >= bufferSize-1) {
+    assert(buffer[bufferSize - 1] == 0);
     return bufferSize-1;
   }
   // For all remaining children:
@@ -61,11 +92,13 @@ int SerializationHelper::Infix(
     // Write the operator
     numberOfChar += strlcpy(buffer+numberOfChar, operatorName, bufferSize-numberOfChar);
     if (numberOfChar >= bufferSize-1) {
+      assert(buffer[bufferSize - 1] == 0);
       return bufferSize-1;
     }
     // Write the child, with parentheses if needed
-    serializeChild(node->childAtIndex(i), node, buffer, bufferSize, floatDisplayMode, numberOfDigits, &numberOfChar);
+    numberOfChar+= serializeChild(node->childAtIndex(i), node, buffer + numberOfChar, bufferSize - numberOfChar, floatDisplayMode, numberOfDigits);
     if (numberOfChar >= bufferSize-1) {
+      assert(buffer[bufferSize - 1] == 0);
       return bufferSize-1;
     }
   }
@@ -84,18 +117,17 @@ int SerializationHelper::Prefix(
     const char * operatorName,
     bool writeFirstChild)
 {
-  // If buffer has size 0 or 1, put a zero if it fits and return
-  if (bufferSize == 0) {
-    return -1;
-  }
-  buffer[bufferSize-1] = 0;
-    if (bufferSize == 1) {
-    return 0;
+  {
+    int result = 0;
+    if (checkBufferSize(buffer, bufferSize, &result)) {
+      return result;
+    }
   }
 
   // Copy the operator name
   int numberOfChar = strlcpy(buffer, operatorName, bufferSize);
   if (numberOfChar >= bufferSize-1) {
+    assert(buffer[bufferSize - 1] == 0);
     return bufferSize-1;
   }
 
@@ -115,6 +147,7 @@ int SerializationHelper::Prefix(
     // Write the first child
     numberOfChar += node->childAtIndex(firstChildIndex)->serialize(buffer+numberOfChar, bufferSize-numberOfChar, floatDisplayMode, numberOfDigits);
     if (numberOfChar >= bufferSize-1) {
+      assert(buffer[bufferSize - 1] == 0);
       return bufferSize-1;
     }
 
@@ -126,6 +159,7 @@ int SerializationHelper::Prefix(
       }
       numberOfChar += node->childAtIndex(i)->serialize(buffer+numberOfChar, bufferSize-numberOfChar, floatDisplayMode, numberOfDigits);
       if (numberOfChar >= bufferSize-1) {
+        assert(buffer[bufferSize - 1] == 0);
         return bufferSize-1;
       }
     }
@@ -138,12 +172,11 @@ int SerializationHelper::Prefix(
 }
 
 int SerializationHelper::Char(char * buffer, int bufferSize, char c) {
-  if (bufferSize == 0) {
-    return -1;
-  }
-  if (bufferSize == 1) {
-    buffer[0] = 0;
-    return 0;
+  {
+    int result = 0;
+    if (checkBufferSize(buffer, bufferSize, &result)) {
+      return result;
+    }
   }
   buffer[0] = c;
   buffer[1] = 0;
@@ -151,12 +184,11 @@ int SerializationHelper::Char(char * buffer, int bufferSize, char c) {
 }
 
 int SerializationHelper::CodePoint(char * buffer, int bufferSize, class CodePoint c) {
-  if (bufferSize == 0) {
-    return -1;
-  }
-  if (bufferSize == 1) {
-    buffer[0] = 0;
-    return 0;
+  {
+    int result = 0;
+    if (checkBufferSize(buffer, bufferSize, &result)) {
+      return result;
+    }
   }
   size_t size = UTF8Decoder::CodePointToChars(c, buffer, bufferSize);
   int nullTerminatingIndex = min(size, bufferSize - 1);