diff --git a/poincare/include/poincare/expression.h b/poincare/include/poincare/expression.h
index ab69edf76..3e32a1dd8 100644
--- a/poincare/include/poincare/expression.h
+++ b/poincare/include/poincare/expression.h
@@ -245,9 +245,9 @@ protected:
 
   /* Properties */
   int getPolynomialCoefficients(Context & context, const char * symbolName, Expression coefficients[]) const { return node()->getPolynomialCoefficients(context, symbolName, coefficients); }
-  bool hasSymbols(Context & context) const;
-  Expression replaceSymbols(Context & context) { return node()->replaceSymbols(context); }
-  Expression defaultReplaceSymbols(Context & context);
+  bool hasReplaceableSymbols(Context & context) const;
+  Expression replaceReplaceableSymbols(Context & context) { return node()->replaceReplaceableSymbols(context); }
+  Expression defaultReplaceReplaceableSymbols(Context & context);
 
   /* Simplification */
   Expression denominator(Context & context, Preferences::AngleUnit angleUnit) const { return node()->denominator(context, angleUnit); }
diff --git a/poincare/include/poincare/expression_node.h b/poincare/include/poincare/expression_node.h
index e41efb86e..e8f559e32 100644
--- a/poincare/include/poincare/expression_node.h
+++ b/poincare/include/poincare/expression_node.h
@@ -106,7 +106,7 @@ public:
   /*!*/ virtual Expression setSign(Sign s, Context & context, Preferences::AngleUnit angleUnit);
   virtual int polynomialDegree(Context & context, const char * symbolName) const;
   /*!*/ virtual int getPolynomialCoefficients(Context & context, const char * symbolName, Expression coefficients[]) const;
-  /*!*/ virtual Expression replaceSymbols(Context & context);
+  /*!*/ virtual Expression replaceReplaceableSymbols(Context & context);
   typedef bool (*isVariableTest)(const char * c);
   virtual int getVariables(Context & context, isVariableTest isVariable, char * variables, int maxSizeVariable) const;
   virtual float characteristicXRange(Context & context, Preferences::AngleUnit angleUnit) const;
diff --git a/poincare/include/poincare/symbol.h b/poincare/include/poincare/symbol.h
index e4abbe1c1..8c82ef03f 100644
--- a/poincare/include/poincare/symbol.h
+++ b/poincare/include/poincare/symbol.h
@@ -31,7 +31,7 @@ public:
 
   /* Simplification */
   Expression shallowReduce(Context & context, Preferences::AngleUnit angleUnit, bool replaceSymbols = true) override;
-  Expression replaceSymbols(Context & context) override;
+  Expression replaceReplaceableSymbols(Context & context) override;
 
   /* Approximation */
   Evaluation<float> approximate(SinglePrecision p, Context& context, Preferences::AngleUnit angleUnit) const override { return templatedApproximate<float>(context, angleUnit); }
@@ -77,7 +77,7 @@ public:
   Expression shallowReduce(Context & context, Preferences::AngleUnit angleUnit, bool replaceSymbols = true);
   Expression replaceSymbolWithExpression(const SymbolAbstract & symbol, const Expression & expression);
   int getPolynomialCoefficients(Context & context, const char * symbolName, Expression coefficients[]) const;
-  Expression replaceSymbols(Context & context);
+  Expression replaceReplaceableSymbols(Context & context);
 private:
   SymbolNode * node() const { return static_cast<SymbolNode *>(Expression::node()); }
 };
diff --git a/poincare/src/expression.cpp b/poincare/src/expression.cpp
index 99f04ef9d..313b7bda3 100644
--- a/poincare/src/expression.cpp
+++ b/poincare/src/expression.cpp
@@ -221,16 +221,19 @@ void Expression::defaultSetChildrenInPlace(Expression other) {
   }
 }
 
-bool Expression::hasSymbols(Context & context) const {
+bool Expression::hasReplaceableSymbols(Context & context) const {
   return recursivelyMatches([](const Expression e, Context & context) {
-      return e.type() == ExpressionNode::Type::Symbol || e.type() == ExpressionNode::Type::Function;
+      return (e.type() == ExpressionNode::Type::Symbol
+          && !context.expressionForSymbol(static_cast<const Symbol &>(e)).isUninitialized())
+      || (e.type() == ExpressionNode::Type::Function
+           && !context.expressionForSymbol(static_cast<const Function &>(e)).isUninitialized());
       }, context);
 }
 
-Expression Expression::defaultReplaceSymbols(Context & context) {
+Expression Expression::defaultReplaceReplaceableSymbols(Context & context) {
   int nbChildren = numberOfChildren();
   for (int i = 0; i < nbChildren; i++) {
-    childAtIndex(i).replaceSymbols(context);
+    childAtIndex(i).replaceReplaceableSymbols(context);
   }
   return *this;
 }
@@ -327,12 +330,12 @@ Expression Expression::ExpressionWithoutSymbols(Expression e, Context & context)
    * symbols are likely to be defined circularly, in which case we return an
    * uninitialized expression.*/
   int replacementCount = 0;
-  while (e.hasSymbols(context)) {
+  while (e.hasReplaceableSymbols(context)) {
     replacementCount++;
     if (replacementCount > k_maxSymbolReplacementsCount) {
       return Expression();
     }
-    e = e.replaceSymbols(context);
+    e = e.replaceReplaceableSymbols(context);
   }
   return e;
 }
diff --git a/poincare/src/expression_node.cpp b/poincare/src/expression_node.cpp
index 574da2145..3b6de93e4 100644
--- a/poincare/src/expression_node.cpp
+++ b/poincare/src/expression_node.cpp
@@ -27,8 +27,8 @@ int ExpressionNode::getPolynomialCoefficients(Context & context, const char * sy
   return Expression(this).defaultGetPolynomialCoefficients(context, symbolName, coefficients);
 }
 
-Expression ExpressionNode::replaceSymbols(Context & context) {
-  return Expression(this).defaultReplaceSymbols(context);
+Expression ExpressionNode::replaceReplaceableSymbols(Context & context) {
+  return Expression(this).defaultReplaceReplaceableSymbols(context);
 }
 
 int ExpressionNode::getVariables(Context & context, isVariableTest isVariable, char * variables, int maxSizeVariable) const {
diff --git a/poincare/src/symbol.cpp b/poincare/src/symbol.cpp
index 5985e4634..294082fab 100644
--- a/poincare/src/symbol.cpp
+++ b/poincare/src/symbol.cpp
@@ -120,8 +120,8 @@ Expression SymbolNode::shallowReduce(Context & context, Preferences::AngleUnit a
   return Symbol(this).shallowReduce(context, angleUnit, replaceSymbols);
 }
 
-Expression SymbolNode::replaceSymbols(Context & context) {
-  return Symbol(this).replaceSymbols(context);
+Expression SymbolNode::replaceReplaceableSymbols(Context & context) {
+  return Symbol(this).replaceReplaceableSymbols(context);
 }
 
 template<typename T>
@@ -202,10 +202,10 @@ int Symbol::getPolynomialCoefficients(Context & context, const char * symbolName
   return 0;
 }
 
-Expression Symbol::replaceSymbols(Context & context) {
+Expression Symbol::replaceReplaceableSymbols(Context & context) {
   Expression e = context.expressionForSymbol(*this);
   if (e.isUninitialized()) {
-    e = Undefined();
+    return *this;
   }
   replaceWithInPlace(e);
   return e;