diff --git a/apps/graph/list/storage_list_controller.cpp b/apps/graph/list/storage_list_controller.cpp
index f92b369d5..f92b24705 100644
--- a/apps/graph/list/storage_list_controller.cpp
+++ b/apps/graph/list/storage_list_controller.cpp
@@ -40,7 +40,7 @@ void StorageListController::renameSelectedFunction() {
 bool StorageListController::textFieldDidFinishEditing(TextField * textField, const char * text, Ion::Events::Event event) {
   // Compute the new name
   size_t textLength = strlen(text);
-  size_t argumentLength = strlen("(x)"); //TODO
+  size_t argumentLength = StorageFunction::k_parenthesedArgumentLength;
   constexpr int maxBaseNameSize = StorageFunction::k_maxNameWithArgumentSize;
   char baseName[maxBaseNameSize];
   if (textLength <= argumentLength) {
diff --git a/apps/shared/storage_function.cpp b/apps/shared/storage_function.cpp
index c4e61318b..36610b5c6 100644
--- a/apps/shared/storage_function.cpp
+++ b/apps/shared/storage_function.cpp
@@ -8,6 +8,8 @@ using namespace Poincare;
 
 namespace Shared {
 
+char StorageFunction::k_parenthesedArgument[]("(x)");
+
 uint32_t StorageFunction::checksum() {
   assert(!isNull());
   return checksum();
@@ -28,16 +30,15 @@ void StorageFunction::setActive(bool active) {
 int StorageFunction::nameWithArgument(char * buffer, size_t bufferSize, char arg) {
   const char * functionName = fullName();
   size_t index = 0;
-  const char ofXSring[4] = {'(',arg,')', 0};
-  size_t ofXSringLength = strlen(ofXSring);
+  k_parenthesedArgument[1] = arg;
   while (*functionName != Ion::Storage::k_dotChar
-      && index < bufferSize - ofXSringLength - 1)
+      && index < bufferSize - k_parenthesedArgumentLength - 1)
   {
     // We keep room to write the final "(x)" //TODO should we?
     assert(functionName < fullName() + strlen(fullName()));
     buffer[index++] = *functionName++;
   }
-  return index + strlcpy(&buffer[index], ofXSring, bufferSize-index);
+  return index + strlcpy(&buffer[index], k_parenthesedArgument, bufferSize-index);
 }
 
 template<typename T>
diff --git a/apps/shared/storage_function.h b/apps/shared/storage_function.h
index aaaf0d535..78dceb8e0 100644
--- a/apps/shared/storage_function.h
+++ b/apps/shared/storage_function.h
@@ -9,7 +9,9 @@ namespace Shared {
 
 class StorageFunction : public StorageExpressionModel {
 public:
-  constexpr static int k_maxNameWithArgumentSize = Poincare::SymbolAbstract::k_maxNameSize + 4; /* Function name and null-terminating char + "(x)" */;
+  constexpr static int k_parenthesedArgumentLength = 3;
+  constexpr static int k_maxNameWithArgumentSize = Poincare::SymbolAbstract::k_maxNameSize + k_parenthesedArgumentLength; /* Function name and null-terminating char + "(x)" */;
+
   // Constructors
   StorageFunction(Ion::Storage::Record record) : StorageExpressionModel(record){}
 
@@ -44,6 +46,7 @@ protected:
     bool m_active;
   };
 private:
+  static char k_parenthesedArgument[k_parenthesedArgumentLength+1];
   template<typename T> T templatedApproximateAtAbscissa(T x, Poincare::Context * context) const;
   FunctionRecordData * recordData() const;
 };