diff --git a/poincare/include/poincare/function.h b/poincare/include/poincare/function.h
index 781324826..c1109f0bd 100644
--- a/poincare/include/poincare/function.h
+++ b/poincare/include/poincare/function.h
@@ -53,15 +53,7 @@ friend class FunctionNode;
 public:
   Function(const FunctionNode * n) : SymbolAbstract(n) {}
   static Function Builder(const char * name, size_t length, Expression child = Expression());
-  static Expression UntypedBuilder(const char * name, size_t length, Expression child, Context * context) {
-    /* Create an expression only if it is not in the context or defined as a
-     * function */
-    Function f = Function::Builder(name, length, child);
-    if (SymbolAbstract::ValidInContext(f, context)) {
-      return f;
-    }
-    return Expression();
-  }
+  static Expression UntypedBuilder(const char * name, size_t length, Expression child, Context * context);
 
   // Simplification
   Expression replaceSymbolWithExpression(const SymbolAbstract & symbol, const Expression & expression);
diff --git a/poincare/include/poincare/symbol.h b/poincare/include/poincare/symbol.h
index fbe668d84..3c4c93ec4 100644
--- a/poincare/include/poincare/symbol.h
+++ b/poincare/include/poincare/symbol.h
@@ -67,14 +67,8 @@ public:
   static Symbol Builder(const char * name, int length) { return SymbolAbstract::Builder<Symbol, SymbolNode>(name, length); }
   static Symbol Builder(char name) { return Symbol::Builder(&name, 1); }
   static Symbol Ans() { return Symbol::Builder(k_ans, k_ansLength); }
-  static Expression UntypedBuilder(const char * name, size_t length, Context * context) {
-    // create an expression only if it is not in the context or defined as a symbol
-    Symbol s = Symbol::Builder(name, length);
-    if (SymbolAbstract::ValidInContext(s, context)) {
-      return s;
-    }
-    return Expression();
-  }
+  static Expression UntypedBuilder(const char * name, size_t length, Context * context);
+
   // Symbol properties
   bool isSystemSymbol() const { return name()[0] == SpecialSymbols::UnknownX && name()[1] == 0; }
   static bool isSeriesSymbol(const char * c);
diff --git a/poincare/src/function.cpp b/poincare/src/function.cpp
index ec7910c85..50ed7e0b2 100644
--- a/poincare/src/function.cpp
+++ b/poincare/src/function.cpp
@@ -100,6 +100,16 @@ Function Function::Builder(const char * name, size_t length, Expression child) {
   return f;
 }
 
+Expression Function::UntypedBuilder(const char * name, size_t length, Expression child, Context * context) {
+  /* Create an expression only if it is not in the context or defined as a
+   * function */
+  Function f = Function::Builder(name, length, child);
+  if (SymbolAbstract::ValidInContext(f, context)) {
+    return f;
+  }
+  return Expression();
+}
+
 Expression Function::replaceSymbolWithExpression(const SymbolAbstract & symbol, const Expression & expression) {
   // Replace the symbol in the child
   childAtIndex(0).replaceSymbolWithExpression(symbol, expression);
diff --git a/poincare/src/symbol.cpp b/poincare/src/symbol.cpp
index f4225c05a..0428218eb 100644
--- a/poincare/src/symbol.cpp
+++ b/poincare/src/symbol.cpp
@@ -139,6 +139,15 @@ Evaluation<T> SymbolNode::templatedApproximate(Context& context, Preferences::Co
   return e.node()->approximate(T(), context, complexFormat, angleUnit);
 }
 
+Expression Symbol::UntypedBuilder(const char * name, size_t length, Context * context) {
+  // create an expression only if it is not in the context or defined as a symbol
+  Symbol s = Symbol::Builder(name, length);
+  if (SymbolAbstract::ValidInContext(s, context)) {
+    return s;
+  }
+  return Expression();
+}
+
 bool Symbol::isSeriesSymbol(const char * c) {
   // [NV][1-3]
   if (c[2] == 0 && (c[0] == 'N' || c[0] == 'V') && c[1] >= '1' && c[1] <= '3') {